Thermal and mechanical properties of bio-based polymer networks by thiol-ene photopolymerizations of gallic acid and pyrogallol derivatives

Allylated pyrogallol (A3PG) and acrylated pyrogallol (Ac3PG) as bio-based trienes, and allylated gallic acid (A4GA) and acrylated allyl gallate (Ac3A1GA) as bio-based tetraenes were synthesized from pyrogallol and gallic acid, respectively. Thiol-ene photopolymerizations of the bio-based polyenes and a pentaerythritol-based primary tetrathiol (pS4P) at the allyl/SH ratio of 1/1 produced photo-cured resins (A3PG-pS4P, Ac3PG-pS4P, A4GA-pS4P and Ac3A1GA-pS4P). The FT-IR spectral analysis revealed that thiol-ene reactions of thiol/allyl and thiol/acryloyl groups smoothly proceeded. Gel fractions of acryl-based cured resins were a little higher than those of allyl-based cured resins. The swelling test and dynamic mechanical analysis revealed that GA- and acryl-based cured resins exhibited higher crosslinking densities than PG- and allyl-based cured resins, respectively. A higher order of tan δ peak temperature was Ac3PG-pS4P (48.3 ° C) > Ac3A1GA-pS4P (24.1 ° C) > A4GA-pS4P (22.1 ° C) > A3PG-pS4P (?7.8 ° C). Ac3PG-pS4P displayed the highest 5 % weight loss temperature, tensile strength and tensile modulus among all of the cured resins.     

Verification and validation of explicit moving particle simulation method for application to internal flooding analysis in nuclear reactor building

The Fukushima nuclear accident raised the importance of flooding study in nuclear reactor buildings. It is known that the external flooding can be attributed to natural causes, while the internal flooding is caused by the piping ruptures, tank failure or the actuation of fire suppression systems. The building flooding process can damage the safety-related components and systems, which needs to study carefully. In order to simulate this phenomenon which is accompanied by complex flow with free surface, a particle method based on Lagrangian approach named explicit moving particle simulation (EMPS) method, is employed in this analysis. Verification and validation analyses are carried out. The verification problems are a hydrostatic analysis and a water spreading to investigate the differences of the particle wall and polygon wall boundary models, while the validation studies of two experiments of dam-break induced flooding show good agreements. Afterwards, the internal flooding process in AP1000 is simulated by assuming a break of the in-containment refueling water storage tank as an example. The results achieved so far indicate that the EMPS method is capable to simulate the internal flooding process in the nuclear reactor buildings.     

Preparation and mesostructure control of highly ordered zirconia particles having crystalline walls

Mesostructured zirconia particles having monoclinic-type crystalline walls were prepared using a low-temperature crystallization technique. Crystalline zirconia particles with highly-ordered mesostructures were obtained through the sol–gel process of zirconium sulfate tetrahydrate at 333 K in the presence of molecular self-assemblies of cetyltrimethylammonium bromide (CTAB) or mixtures of CTAB and anionic molecules such as sodium dodecyl sulfate and sodium p-toluenesulfonate. Variations in the molar ratios of CTAB and the chemical species of anionic molecules led to the variations in the periods of highly-ordered zirconia having crystalline walls. Calcination of the mesostructured zirconia particles prepared using templates consisting solely of CTAB yielded crystalline mesoporous zirconia particles.     

Thermosetting bismaleimide resins generating covalent and multiple hydrogen bonds

Prepolymerizations of 4,4′‐bismaleimidodiphenylmethane (BMI), diallyl isocyanurate (DAIC), and melamine (ML) at 160–170°C and subsequent compression molding at 200–280°C yielded cured BMI/DAIC/ML resins with feed molar ratios of 4/1/1, 3/1/1, and 2/1/1 (BMI‐DAIC‐ML411, 311, and 211). Similarly, cured BMI/DAIC 1/1 and BMI/ML 3/1 resins (BMI‐DAIC11 and BMI‐ML31) were prepared. The FT‐IR analysis revealed that the maleimide and allyl groups were almost consumed for all the cured resins, and the hydrogen bonding interaction became stronger with decreasing BMI contents for BMI‐DAIC‐MLs. Based on the cured structures elucidated from the FT‐IR result, the numbers of multiple hydrogen bonds and cross‐linking covalent bonds (N_MHB and N_CB), and total cross‐linking bond energy (E_TB) were evaluated to be 0, 7.92, and 618 for BMI‐DAIC‐ML411, 0.71, 7.81, and 627 for BMI‐DAIC‐ML311, and 0.95 mol kg^?1, 7.61 mol kg^?1, and 617 kcal kg^?1 for BMI‐DAIC‐ML211, respectively. A higher order of glass transition and 5% weight loss temperatures for BMI‐DAIC‐MLs was 411 > 311 > 211 in accordance with a higher order of N_CB. BMI‐DAIC‐MLs displayed a weak tan δ peak at 70–150°C due to dissociation of the hydrogen bonds. The flexural strength and modulus of BMI‐DAIC‐ML311 were higher than those of BMI‐DAIC‐ML411 in accordance with the difference of E_TB. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43121.     

Mechanical role of reinforcement in seismic behavior of steel-strip reinforced earth wall

In the current design practices of steel-strip reinforced earth walls (SSREWs), the length of the reinforcing material is determined based on the equilibrium between the reinforcement tension and the earth pressure acting on the wall. Here, the resistance of the reinforcing material laid in the active failure zone (AFZ) is not considered. Moreover, the mechanical role of the reinforcing material against the integrity of the SSREW has not been sufficiently verified. Regarding the seismic stability of SSREW, although it is investigated by treating the entire reinforced earth wall as a rigid body, this inspection method is for gravity-retaining walls, and the difference in the seismic behavior between the SSREW and the rigid body is not clear. In this study, therefore, dynamic centrifuge model tests on 6 types of SSREWs were conducted to clarify the following items: (1) the basic earthquake behavior of a SSREW, (2) the mechanical role of the reinforcing material laid in the AFZ and (3) the mechanical role of the reinforcing material against the integrity of the SSREW. The results indicated that the reinforcing material laid in the AFZ can restrain the amount of deformation of the wall during earthquakes. Furthermore, the more stable the AFZ is, the smaller the maximum wall displacement will be.     

Surface Analysis of Cr2O3‐, CoO‐, and Al2O3‐Doped Iron–Phosphate Glasses at High Temperature

Surface structures of iron–phosphate glasses were examined using X‐ray photoelectron spectroscopy (XPS). Cr₂O₃, CoO, and Al₂O₃ were introduced to the glass by the replacement of a part of Fe₂O₃, and the simulated fission products are also added. The obtained glasses showed high chemical durabilities by MCC‐1 test. In situ high‐temperature and room‐temperature XPS measurements were conducted on the polished sample surfaces and also those after 1‐week chemical durability test. Unique trends were observed in XPS spectra on heating and after the chemical durability test, respectively. Nature of the glass surface of iron–phosphate glasses was explained from the point of view of surface energy, and the origin of high chemical durability and the effect of chromium ions were discussed based on the changes on surface composition and valence states of transition‐metal ions.     

Bactericidal effect of cationic hydrogels prepared from hydrophilic polymers

This study investigated whether hydrogels comprising hydrophilic cationic polymers have similar bactericidal effects. Bacteria were seeded on hydrogels and agar and their viability was assessed with time. Cationic hydrogels displayed bactericidal effects upon long-term bacterial contact. Furthermore, we assessed the areal density of cationic monomer unit of the cationic hydrogels, water content, and the initial elastic modulus. We examined correlations between each factor and bacterial death ratios; consequently, the bacterial death ratios were strongly correlated with the areal density of cationic hydrogel monomers. Elastic energy (W_el) generated at the cytomembrane ion-binding region and the cationic hydrogel and the cytomembrane interfacial energy (W_f) were estimated; consequently, W_el exceeded W_f at higher contact areas. The cationic hydrogel may extract cytomembranes with a reasonable adsorption area. Therefore, cationic hydrogels may be used as probes for ultrasonic echo to sterilize medical equipment.     

Development of copper beam ducts with antechambers for advanced high-current particle storage rings

There has been continuous progress at the High Energy Accelerator Research Organization (KEK) in R&D on vacuum beam ducts adaptable to future high-current particle storage rings. Here we proposed copper beam ducts with antechambers to deal with the severe issues attributed to the high beam currents. The proposed antechamber scheme can withstand intense synchrotron radiation (SR), provide a beam duct with low beam impedance, and effectively reduce the electron cloud effect (ECE) in positron/proton rings. Several trial models were manufactured by a pressing or cold-drawn method, and assembled with electron beam welding. Special vacuum components, such as connection flanges, distributed pumps, and gate valves, were customized for the beam ducts. TiN coating on the inner surface of the beam duct was also investigated as a mitigating measure for the ECE. Trial models of the copper beam ducts were installed into the KEK B-factory (KEKB), and their performances were evaluated using real positron and electron beams.     

EFFECTS OF OPERATIONAL CONDITIONS ON DRYING CHARACTERISTICS IN CLOSED SUPERHEATED STEAM DRYING

The effects of operational conditions on the drying performance in closed superheated steam drying were examined theoretically and experimentally. The vapor generated from the sample was circulated in the drying chamber. In the theoretical analysis, the replacement of air with vapor in drying chamber and the convective vapor transfer in sample were considered. At the start of drying, the drying chamber was filled with air. As the drying proceeded, the air was replaced with the vapor generated from sample. The calculated results explained the characteristics of experimental data. The pore diameter of sample had little effect on the drying characteristics. During the internal evaporation period, the evaporation occurred in the narrow zone, which moved from the surface to the bottom of sample. The convective vapor transfer in sample had a significant influence on the drying performance. The excess increments in temperature and velocity of drying gas hardly contributed to shortening the drying time.