Simulation of the fracture behavior of Zircaloy-4 cladding under reactivity-initiated accident conditions with a damage mechanics model combined with fuel performance codes FEMAXI-7 and RANNS

A continuum damage mechanics model using FEM calculations was proposed to be applied to an analysis of the fuel failure due to pellet cladding mechanical interaction (PCMI) under reactivity-initiated accident conditions. The model expressed ductile fracture via two processes: damage nucleation related to void nucleation and damage evolution related to void growth and linkage. The boundary conditions for the simulations were input from the fuel performance codes FEMAXI-7 and RANNS. The simulation made reasonable predictions for the cladding hoop strain at failure and reproduced the typical fracture behavior of the fuel cladding under the PCMI loading, characterized by a ductile shear zone in the inner region of the cladding wall. It was shown that occurrence of a through-wall crack is determined at an early stage of crack propagation, and the rest of the through-wall penetration process is achieved with a negligible increment in strain. The effect of a local temperature rise in the cladding inner region on the failure strain was found to be less than 5% for the conditions investigated. Failure strains predicted under a plane strain loading were smaller by 20%–30% than those predicted under equibiaxial tensions between the hoop and the axial directions.     

Controllable electrode activities of nano-carbon films while maintaining surface flatness by electrochemical pretreatment

A carbon film consisting nanocrystallites with mixed sp² and sp³ bonds formed by using the electron cyclotron resonance (ECR) sputtering method was studied with respect to the changes in characteristics caused by electrochemical pretreatment (ECP). Unlike glassy carbon, our sputtered nanocrystalline carbon film deposited at an acceleration voltage of 75 V (ECR-75 nano-carbon film) largely retained its surface flatness after the ECP. This robust surface could be caused by an increase of 42% in the sp³ carbon realized by increasing the acceleration voltage during sputtering. The electrode activity of ECR-75 nano-carbon film was improved for surface sensitive species including Fe^3+/2+ unlike the boron doped diamond (BDD) electrode. This is because a sufficient quantity of surface sp² bonds remained and because the introduction of surface oxygen-containing groups is more efficient than with the BDD electrode. With pretreated ECR-75 nano-carbon film, the peak potential of glutathione was reduced solely due to the increase in the surface hydrophilicity with a sufficient quantity of surface sp² bonds, thus achieving the lowest detection limit (0.4 μM) ever obtained with carbon electrodes. We also achieved the stable measurement of 30 μM of serotonin (20 times) without the electrode surface fouling found with other electrodes.     

Electrophoretic cell manipulation and electrochemical gene-function analysis based on a yeast two-hybrid system in a microfluidic device

A novel microfluidic device with an array of analytical chambers was developed in order to perform single-cell-based gene-function analysis. A series of analytical processes was carried out using the device, including electrophoretic manipulation of single cells and electrochemical measurement of gene function. A poly(dimethylsiloxane) microstructure with a microfluidic channel (150 microm in width, 10 microm in height) and an analytical chamber (100 x 20 x 10 microm (3)) were fabricated and aligned on a glass substrate with an array of Au microelectrodes. Two microelectrodes positioned in the analytical chamber were employed as a working electrode for the electrophoretic manipulation of cells and electrochemical measurements. A yeast strain ( Saccharomyces cerevisiae Y190) carrying the beta-galactosidase reporter gene was used to demonstrate that the device could detect the enzyme. Target cells flowing through the main channel were introduced into the chamber by electrophoresis using the ground electrode laid on the main channel. When the cell was treated with 17beta-estradiol, gene expression was triggered to produce beta-galactosidase, catalyzing the hydrolysis of p-aminophenyl-beta- D-galactopyranoside to form p-aminophenol (PAP). The enzymatically generated PAP was detected by cyclic voltammetry and amperometry at the single-cell level in the chamber of the device. Generator-collector mode amperometry was also applied to amplify the current response originating from gene expression in the trapped single cells. After electrochemical measurement, the trapped cells were easily released from the chamber using electrophoretic force.     

A multi-walled carbon nanotube/polymer actuator that surpasses the performance of a single-walled carbon nanotube/polymer actuator

Actuators were developed using activated and non-activated multi-walled carbon nanotube (MWCNT)–ionic liquid (IL) gel electrodes and compared to a single-walled carbon nanotube (SWCNT)-based actuator with respect to the electrochemical and electromechanical properties. The activated MWCNT–COOH/polymer actuator surpassed the SWCNT/polymer actuator in terms of the generated strain.     

Photoinduced Magnetization with a High Curie Temperature and a Large Coercive Field in a Co‐W Bimetallic Assembly

The crystal structure, magnetic properties, and temperature‐ and photoinduced phase transition of [{Co^II(4‐methylpyridine)(pyrimidine)}₂{Co^II(H₂O)₂}{W^V(CN)₈}₂]·4H₂O are described. In this compound, a temperature‐induced phase transition from the Co^II (S = 3/2)‐NC‐W^V(S = 1/2) [high‐temperature (HT)] phase to the Co^III(S = 0)‐NC‐W^IV(S = 0) [low temperature (LT)] phase is observed due to a charge‐transfer‐induced spin transition. When the LT phase is irradiated with 785 nm light, ferromagnetism with a high Curie temperature (T_C) of 48 K and a gigantic magnetic coercive field (H_c) of 27 000 Oe are observed. These T_C and H_c values are the highest in photoinduced magnetization systems. The LT phase is optically converted to the photoinduced phase, which has a similar valence state as the HT phase due to the optically induced charge‐transfer‐induced spin transition.     

Bactericidal effects of konjac fluid on several food-poisoning bacteria

In this study, the bactericidal effects of Japanese alkaline foods on food-poisoning bacteria were evaluated. Konjac is an alkaline food soaked in calcinated calcium (the pH of konjac fluid ranges from 11.42 to 12.53). Konjac fluids completely inactivated Escherichia coli, enterohemorrhagic E. coli O157:H7 and E. coil O26:H9, Salmonella Enteritidis, Vibrio parahemolyticus. and Staphylococcus aureus. The initial level of 6 log CFU/ml dramatically decreased after incubation with konjac fluid, and no viable gram-negative bacterium cells could be detected within 1 to 2 days and no viable S. aureus cells could be detected within 3 to 5 days. On the other hand, treatment with konjac fluid was also effective in reducing levels of spore-forming bacteria (Bacillus subtilis, Bacillus cereus, Clostridium perfringens, and Clostridium botulinum type E and type A). At least a 4-log reduction of spore-forming bacteria was obtained in konjac fluid within 7 to 14 days. Vegetative cells were more susceptible to konjac fluid than spores were. When the initial cell count was 6 log CFU/ml, a few surviving spores remained for 60 to 90 days, but no spores could be detected after 120 days. When the initial count of spore-forming bacteria was 3 to 4 log CFU/ml, the cells considered vegetative were completely inactivated within I to 3 days. Repeated treatment with konjac fluid caused complete inactivation of spores in less than 1 to 3 days. Our studies indicate that konjac fluid, which has a long history of use in food, will control food-poisoning bacterial contamination during the production or preservation of konjac and other foods and has a preventive effect on bacteria that can cause severe disease at uniquely low levels.     

In situ binary sol–gel reaction of various trifunctional alkoxysilane in the silane‐grafted polyolefin matrix and its effect upon the mechanical properties

The vinyltrimethoxysilane‐grafted ethylene‐propylene copolymer/trifunctional methoxysilane (EPR‐g‐VTMS/RTMS) composites were prepared via in situ silica sol–gel reactions. Five trifunctional methoxysilane compounds (n‐hexyltrimethoxysilane, n‐decyltrimethoxysilane, n‐tetradecyltrimethoxysilane, n‐octadecyltrimethoxysilane, and phenyltrimethoxysilane) have been selected for this study. The water‐cross‐linked EPR‐g‐VTMS/RTMS composites were characterized by attenuated total reflectance‐Fourier transform infrared spectroscopy, gel content, solid‐state ²⁹Si CP/MAS NMR, wide‐angle x‐ray scattering, tensile strength, and field emission scanning electron microscopy measurements. The type of RTMS additive has a substantial influence on the nature of siloxane band networks and eventually the mechanical tensile properties. This finding suggests that the interaction and/or entanglement between the EPR‐g‐VTMS matrix and the substituent of the RTMS additives are crucial for the modifying mechanical properties. Moreover, for the water‐cross‐linked EPR‐g‐VTMS/CnTMS (n = 6, 10, 14, and 18) composites, the joint evidence provided by attenuated total reflectance‐Fourier transform infrared spectroscopy, ²⁹Si CP/MAS NMR, and wide‐angle x‐ray scattering results suggested the formation of ladder‐type poly(n‐alkyl silsesquioxane)s and the presence of the highly ordered structure with a thickness equal to the length of two n‐alkyl groups in all‐trans conformation. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.     

Adhesion Properties of Acrylic Copolymers Modified with Si-Containing Copolymer

We made clear the cause of the increase in peel strength of pressure sensitive (PS) adhesives as a function of contact time, and investigated how to modify PS adhesives to maintain a low and constant peel strength for a long time. It was found that polar groups in the adhesive orient to the interface between the adhesive and the (stainless steel) metal substrate (SUS 304) so as to minimize interfacial free energy during adhesion, and the orientation increased affinity between the adhesive and the metal material and increased the peel strength as a result. The use of modifier which contained both P(MMA-co-SiMA) and PDMS showed an excellent modification effect, although modification with only PDMS or P(MMA-co-SiMA) was not sufficient. It was suggested that PDMS which migrated to the surface was extended uniformly over the surface by PDMS segments of P(MMA-co-SiMA) and that the enriched layer of PDMS on the adhesive surface worked as a barrier to prevent the orientation of polar groups in bulk. Therefore, low and constant peel strength could be achieved.     

通过CBT方法开发低热输入低飞溅CO2/MAG交流焊接系统

OTC(DAIHEN Corporation)公司新研发的CBT焊接控制法实现了GMA焊接的低飞溅和低热输入,特别是针对薄板,进一步提高了薄板的焊接性能,这对早期的传统焊接控制技术来说是很难实现的.通过调节负极占空比,交流CBT控制法能够实现改变焊接过程中的熔深和熔敷量,有效避免了薄板焊接中的烧穿和降低热变形问题.新开发的反抽起弧控制确保了起弧的成功率并有效拟制飞溅的发生.