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To overcome the aggregation of porphyrins and realize heterogeneous catalysis with high active site loadings, twisted ZnTHP–Me2Si and layered ZnTHP–Ph2Si are synthesized by cross-linking 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin zinc (ZnTHP) respectively with dichlorodimethylsilane and dichlorodiphenylsilane. The microstructures of both ZnTHP–Me2Si and ZnTHP–Ph2Si are investigated, and their active site loadings were found to be greater than 0.8 mmol ZnTHP per g ZnTHP-Me2Si or per g ZnTHP-Ph2Si. Furthermore they act as photocatalysts in the photoinduced electron transfer reversible addition–fragmentation chain transfer (PET-RAFT) polymerization of N-isopropyl acrylamide (NIPAm) under green light. The results indicate that both of them show more effective photocatalytic performance than ZnTHP and demonstrate the attractive features of living polymerization. Moreover, twisted ZnTHP–Me2Si with a larger surface area and pore distribution can accelerate the polymerization of NIPAm more effectively. According to the MALDI-TOF analysis, the dispersity of the as-synthesized poly(N-isopropyl acrylamide) (PNIPAm) catalyzed by ZnTHP–Me2Si is less than 1.100 and the minimum value can reach 1.049. The excellent recyclability of ZnTHP–Me2Si is also confirmed by repeated PET-RAFT polymerization cycles, albeit with a slight reduction of the catalyst activity. Therefore PET-RAFT polymerization mediated by cross-linked ZnTHP is a potential method to synthesize a thermo-sensitive polymer with a super narrow molecular weight distribution.

To improve the performance and efficiency of an X-ray source in ordinary X-ray digital radiation imaging system (OXDRIS), parallel-polycapillary optics, in which a divergent X-ray beam can be modulated into a quasi-parallel beam, is introduced in the OXDRIS. The properties of the X-ray beam including beam intensity and divergence are then studied in polycapillary-optics-coupled X-ray DR imaging system (POXDRIS). Furthermore, the characteristics of a digital radiation (DR) image including spatial resolution and contrast are discussed using the POXDRIS. The intensity of the X-ray beam has been increased thirtyfold compared to the OXDRIS without the parallel-polycapillary optics. Moreover, a quasi-parallel beam with a divergence of 2.2 mrad is obtained. The results of the preliminary numerical analysis show that the image contrast and anti-noise performance are enhanced. As the energy range and spatial resolution are influenced by the material used and principle of the polycapillary, the approach should be employed carefully.

In Micro-CT (Computed Tomography) system, a series of projection data of sample are collected by the detector as the precision stage rotates step by step. However, the accuracy of projection images is limited by rotation errors during the acquisition process. Therefore, evaluating the performance of precision rotary stage and developing corresponding compensation method are necessary in Micro-CT system. In this paper, a metered system is designed which is composed of four precision capacitive sensors, a precision machined steel cylinder and four flexible hinges. Based on the metered system, a method to calibrate and correct the errors when the precision stage turns is proposed. Firstly, the theoretical analysis is proposed and the imperfect situations are considered. And then, the method has been applied to correct experimental data taken from a microscope type of Micro-CT system. Successful results are shown through evaluating MTF (Modulation Transfer Function) of Micro-CT system. Lastly, a sample of tungsten wire is scanned and the reconstructed images are compared before and after using the calibrated method.

In our report, a fibrous ceramics with the mullite fibers as the matrix and SiO 2 –AlPO 4 sol as the high-temperature binder were fabricated by the infiltration method. The effects of sintering temperature on the properties, such as porosity, phase transition, microstructure, compressive strength and fracture mechanism, were investigated. Compared with the fibrous ceramics with the SiO 2 –B 2 O 3 binder, the fibrous ceramics with the SiO 2 –AlPO 4 binder exhibited lower densities (0.560–0.595 g/cm 3 ), lower thermal conductivities (0.157–0.165 W/mK), high strain (7–8%), high rebound-resilience (77–90%) and the same level of compressive strengths (1.1–2.1 MPa). During the cooling stage of the heat treatment process, α→β-cristobalite displacive phase transition in the SiO 2 –AlPO 4 binder was successfully suppressed. The fracture behavior of the ceramics tends to be a layer-by-layer failure, which is quite different from that of the traditional ceramics. The non-brittle fracture mode and the excellent elasticity made this fibrous ceramics promising high-temperature elastic insulation materials.

Dual-energy x-ray technique, which consists in combining two radiographs acquired at two kilovoltage, can improve the identity of the compositions of object over regular CT, or at least improve image contrast. Dual-energy equations can be easily written and solved for ideally monochromatic x-ray source and perfect detector, but become complex when considering polychromatic x-ray source, detector sensitivity, and system non–linearity. In this paper, a new dual-energy algorithm which employed the basis material decomposition method was investigated for improving material separation capability. Studies by using computer-simulated data were performed to validate and evaluate the algorithm. The preliminary results of the study show that, with the proposed algorithm, separated “material specific” images of dual-material object could be obtained. Also monochromatic image can be acquired at arbitrary desired energy which could enhance image contrast in comparison with conventional reconstructed image.