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Dao-Hui Xiang,Zhi-Meng Zhang,Bang-Fu Wu,Hao-Ren Feng,Zhan-Li Shi,Bo Zhao 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.11
Silicon carbide particle-reinforced aluminum matrix composite has been widely used in the military and aerospace industry due to its special performance; however, there remain many problems in processing. The present paper introduces an ultrasonic vibration tensile device with a view to investigating an ultrasonic vibration tensile specimen. The results show that there are three major stages in the change in stress of the material under ultrasonic vibration: the ultrasonic stress superposition effect, softening effect, and Hall–Petch strengthening effect, these three effects occupy different proportions in different tensile stages. In addition, increasing the frequency of ultrasonic vibration increased the degree of stress reduction. Increasing the ultrasonic vibration amplitude reduced the fracture strength of the material. Comparison of the fracture morphology shows that the conventional condition was mainly interfacial peeling of SiC particles, and cleavage of the fracture occurred under ultrasonic vibration conditions.
Membrane Biofouling of Seawater Reverse Osmosis Initiated by Sporogenic Bacillus Strain
Jin Wook Lee,Xiang Hao Ren,Hye Weon Yu,Sung Jo Kim,In S. Kim 대한환경공학회 2010 Environmental Engineering Research Vol.15 No.3
The objective of this study was to assess the biofouling characteristics of the Bacillus biofilm formed on reverse osmosis (RO) membranes. For the study, a sporogenic Bacillus sp. was isolated from the seawater intake to a RO process, with two distinct sets of experiments performed to grow the Bacillus biofilm on the RO membrane using a lab-scale crossflow membrane test unit. Two operational feds were used, 9 L sterile-filtered seawater and 10(9) Bacillus cells, with flow rates of 1 L/min, and a constant 800 psi-pressure and pH 7.6. From the results, the membrane with more fouling, in which the observed permeate flux decreased to 33% of its initial value, showed about 10 and 100 times greater extracellular polymeric substances and spoOA genes expressions, respectively, than the those of the less fouled membrane (flux declined to 20% of its initial value). Interestingly; however, the number of culturable Bacillus sp. in the more fouled membrane was about 10 times less than that of the less fouled membrane. This indicated that while the number of Bacillus had less relevance with respect to the extent of biofouling, the activation of the genes of interest, which is initiative of biofilm development, had a more positive effect on biofouling than the mass of an individual Bacillus bacterium.
Immobilization of Lactase onto Various Polymer Nanofibers for Enzyme Stabilization and Recycling
( Li Hua Jin ),( Ye Li ),( Xiang Hao Ren ),( Jung Heon Lee ) 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.8
Five different polymer nanofibers, namely, polyaniline nanofiber (PANI), magnetically separable polyaniline nanofiber (PAMP), magnetically separable DEAE cellulose fiber (DEAE), magnetically separable CM cellulose fiber (CM), and polystyrene nanofiber (PSNF), have been used for the immobilization of lactase (E.C. 3.2.1.23). Except for CM and PSNF, three polymers showed great properties. The catalytic activities (kcat) of the free, PANI, PAMP, and magnetic DEAE-cellulose were determined to be 4.0, 2.05, 0.59, and 0.042 mM/min·mg protein, respectively. The lactase immobilized on DEAE, PANI, and PAMP showed improved stability and recyclability. PANI- and PAMP-lactase showed only a 0-3% decrease in activity after 3 months of vigorous shaking conditions (200 rpm) and at room temperature (25oC). PANI-, PAMP-, and DEAE-lactase showed a high percentage of conversion (100%, 47%, and 12%) after a 1 h lactose hydrolysis reaction. The residual activities of PANI-, PAMP-, and DEAE-lactase after 10 times of recycling were 98%, 96%, and 97%, respectively.