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Hydrogen Bubble Characteristics during a Water - Sodium Leak Accident in a Steam Generator
Park, Jin Ho,Kim, Byung Ho,Hwang, Sung Tai,Kim, Tae Joon,Yughay, Valery S .,Choi, Chung Song 한국공업화학회 2000 Journal of Industrial and Engineering Chemistry Vol.6 No.6
Hydrogen bubble characteristics, the parameters of a defect in a steam generator heat-transfer tube, resonant frequencies and initial bubble radii can all be experimentally calculated using micro-leak rates resulting from a water/steam-into-liquid-sodium injection. The conditions of this experiment were sodium temperatures of 300, 400, and 500℃ and water injection rates of 0.005, 0.03, 0.08, and 0.183 g/sec. The acoustic spectra and hydrogen bubble frequency for a leak rate of 0.005 g/s were measured. Thereafter, the initial radius of hydrogen bubbles was estimated from the acoustic noise spectra and the frequency of the hydrogen bubbles in sodium. Since the lifetime of hydrogen bubbles with a radius of about 3 mm was not more than 3 sec, the acoustic detection of a water/steam-into-sodium leak accident in a KALIMER (Korea Advanced Liquid Metal Reactor) steam generator can satisfy the safety requirements.
High School Students' Perceived Creativity Self-efficacy and Emotions in a Service Learning Context
Ai-Girl Tan,Valerie Ho,Elizabeth Ho,Steve Ow 대한사고개발학회 2008 The International Journal of Creativity & Problem Vol.18 No.2
Our study examined the relationship of creativity self-efficacy and emotions of high school students (n = 279) in Singapore before and after they attended a three to five-day international service learning program. Participants completed a creativity self efficacy scale, the Positive Affect and Negative Affect Scale (PANAS), Satisfaction With Life Scale (SWLS) and Subjective Happiness Scale (SHS). We found a positive, significant correlation between creativity efficacy and positive affect, life satisfaction and subjective happiness but negative correlation with negative mood affect. In addition, students whose creativity efficacy was moderately high were found to have reported higher ratings of life satisfaction after having participated in service learning. Our findings provide initial evidence suggesting that service learning with positive intervention is positively related to creativity self-efficacy and happiness of youth.
Metal-Free Room-Temperature Vulcanization of Silicones via Borane Hydrosilylation
Sample, Caitlin S.,Lee, Sang-Ho,Li, Shaoguang,Bates, Morgan W.,Lensch, Valerie,Versaw, Brooke A.,Bates, Christopher M.,Hawker, Craig J. American Chemical Society 2019 Macromolecules Vol.52 No.19
<P>Vulcanization of silicone networks from commercially available linear poly(dimethyl-<I>co</I>-methylhydro)siloxane (PMHS) and α-diketones was achieved using metal-free borane hydrosilylation at room temperature. The Lewis acid catalyst, tris(pentafluorophenyl)borane (B(C<SUB>6</SUB>F<SUB>5</SUB>)<SUB>3</SUB>), efficiently cross-linked PMHS at minimal catalyst loadings (200-1000 ppm) to produce polymer networks with mechanical properties, thermal stability, and optical clarity rivaling that achieved from traditional platinum catalysis. Variation of the starting PMHS structure is shown to influence the final characteristics of the network. Increasing molar mass of the PMHS chain results in a higher thermal decomposition temperature, while increasing mole fractions of Si-H moieties along the backbone increase the cross-linking density and the attendant Shore hardness. The degradation behavior of the networks was investigated, with the borane-vulcanized samples showing rapid dissolution upon exposure to acid and high stability to neutral and basic conditions. Functional networks bearing halide and vinyl groups could also be prepared via a preliminary reaction of PMHS with an appropriate monoketone, providing a general and versatile strategy for network derivatization with the potential for postvulcanization functionalization being subsequently demonstrated via thiol-ene click chemistry.</P> [FIG OMISSION]</BR>