SYNOPSISHomo-and copolymerization of ethylene were performed by using a catalyst system composedof TiC1,/THF/MgC12 complex activated with A1Et3 at 70°C and 3 atm. T o investigate the effect of the compositional difference of the catalyst on the rates of homo-and copolymerization and on the reactivity in ethylene-hexene copolymerization, a series of six catalysts with different compositions ( Mg/Ti = 0.4-16.5) were prepared by coprecipitation. The catalytic activity in ethylene polymerization increased sharply with the Mg/Ti ratio from 21 (Mg/Ti = 0.4) to 1477 kg PE/g-Ti h (Mg/Ti = 16.5). The activity in copolymerization with 1-hexene also increased with Mg/Ti ratio. The values of rl were 120, regardless of Mg/Ti ratios within the experimental error range. Enhancement of the polymerization rate by the addition of l-hexene in the reaction medium was observed only for the catalysts of low Mg/Ti ratio. This unusual effect of 1-hexene on the polymerization rate was explained by chemical and physical processes that occurred during polymerization.

In this study, sono-assisted dilute sulfuric acid process was evaluated for its viability of simultaneous pretreatment and saccharification of rice straw. Three critical factors for simultaneous pretreatment and saccharification process, such as sonication time (30-50 min), temperature (70-90°C), and acid concentration (5-10 %), were optimized to maximize reducing sugar yield using Box-Behnken design and response surface methodology. The response surface methodology model was found to be adequately fitted to the obtained data. Simultaneous pretreatment and saccharification factors were optimized at sonication of 50 min, 80°C and an acid concentration of 10 % yielding the maximum sugar content (31.78 g/100 g of biomass). Scanning electron microscopy revealed that the smooth surface of raw biomass was altered into a rough and porous surface as a result of sugar release, which showed the prospective feasibility of simultaneous pretreatment and saccharification process. This process integration may lead to develop economical bioethanol production facility. However, further research is required to make this process industrially viable.

Purpose: In computed tomography (CT) imaging, radiation dose delivered to the patient is one of the major concerns. Sparse‐view CT takes projections at sparser view angles and provides a viable option to reducing dose. However, a fast power switching of an X‐ray tube, which is needed for the sparse‐view sampling, can be challenging in many CT systems. We have earlier proposed a many‐view under‐sampling (MVUS) technique as an alternative to sparse‐view CT. In this study, we investigated the effects of collimator parameters on the image quality and aimed to optimize the collimator design. Methods: We used a bench‐top circular cone‐beam CT system together with a CatPhan600 phantom, and took 1440 projections from a single rotation. The multi‐slit collimator made of tungsten was mounted on the X‐ray source for beam blocking. For image reconstruction, we used a total‐variation minimization (TV) algorithm and modified the backprojection step so that only the measured data through the collimator slits are to be used in the computation. The number of slits and the reciprocation frequency have been varied and the effects of them on the image quality were investigated. We also analyzed the sampling efficiency: the sampling density and data incoherence in each case. We tested three sets of slits with their number of 6, 12 and 18, each at reciprocation frequencies of 10, 30, 50 and 70 Hz/ro. Results: Consistent results in the image quality have been produced with the sampling efficiency, and the optimum condition was found to be using 12 slits at 30 Hz/ro. As image quality indices, we used the CNR and the detectability. Conclusion: We conducted an experiment with a moving multi‐slit collimator to realize a sparse‐sampled cone‐beam CT. Effects of collimator parameters on the image quality have been systematically investigated, and the optimum condition has been reached.