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Kang, Zhuang,Zhang, Cheng,Chang, Rui,Ma, Gang The Society of Naval Architects of Korea 2019 International Journal of Naval Architecture and Oc Vol.11 No.2
The numerical simulations for the Vortex-induced Vibration (VIV) of the cylinders with different combinations of mass ratio and frequency ratio were performed under the Reynolds (Re) number ranges of 1450-10200, 5800-40800 and 13050-91800 by using the embedded programs in OpenFoam. By combining with the modified SST k-ω turbulence model, the coupled Unsteady Reynolds-Average Navier-Stokes equations and double-degree-of-freedom vibration equations were solved. After analyzing the results, it is found that the some characteristics of the VIV have changed with the increase of the range of Re number, and the effects of Re number on vibration characteristics are also different under different combinations of mass ratio and frequency ratio. On this basis, the influence law of Re number on the characteristics of VIV of the cylinders is summarized, which can provide a reference for the research of VIV under higher Re number.
Zhuang Kang,Cheng Zhang,Rui Chang,Gang Ma 대한조선학회 2019 International Journal of Naval Architecture and Oc Vol.11 No.2
The numerical simulations for the Vortex-induced Vibration (VIV) of the cylinders with different combinations of mass ratio and frequency ratio were performed under the Reynolds (Re) number ranges of 1450e10200, 5800e40800 and 13050e91800 by using the embedded programs in OpenFoam. By combining with the modified SST k u turbulence model, the coupled Unsteady Reynolds-Averaged NaviereStokes equations and double-degree-of-freedom vibration equations were solved. After analyzing the results, it is found that the some characteristics of the VIV have changed with the increase of the range of Re number, and the effects of Re number on vibration characteristics are also different under different combinations of mass ratio and frequency ratio. On this basis, the influence law of Re number on the characteristics of VIV of the cylinders is summarized, which can provide a reference for the research of VIV under higher Re number.
Kang Liu,Guoming Chen,Gaogeng Zhu,JINGYU ZHUANG 대한조선학회 2019 International Journal of Naval Architecture and Oc Vol.11 No.1
Marine production strings are continuously affected by unstable internal fluid during operation. In this paper, the structural governing equation for marine production string self-induced vibration is constructed. A finite element analysis model is established based on Euler-Bernoulli theory and solved by the Newmark method. Furthermore, based on reliability theory, a self-design procedure is developed to determine the operability envelope for marine production string self-induced vibration. Case studies show: the response frequency of the production strings is consistent with the excitation frequency under harmonic fluctuation and mainly determined by the first-order natural frequency under stochastic fluctuation. The operability envelope for marine production string self-induced vibration is a near symmetrical trapezium. With the increasing of natural gas output, the permissible fluctuation coefficient dramatically decreases. A reasonable centralizer spacing, increasing top tension, and controlling natural gas output are of great significance to the risk control in marine production string operation.
( Kang Wook Lee ),( Jae Min Shim ),( Zhuang Yao ),( Jeong A Kim ),( Hyun-jin Kim ),( Jeong Hwan Kim ) 한국미생물생명공학회(구 한국산업미생물학회) 2017 Journal of microbiology and biotechnology Vol.27 No.7
To develop starters for the production of functional foods or materials, lactic acid bacteria producing γ-aminobutyric acid (GABA) were screened from jeotgals, Korean fermented seafoods. One isolate producing a high amount of GABA from monosodium L-glutamate (MSG) was identified as Enterococcus avium by 16S rRNA gene sequencing. E. avium M5 produced 18.47 ± 1.26 mg/ml GABA when incubated for 48 h at 37℃ in MRS broth with MSG (3% (w/v)). A gadB gene encoding glutamate decarboxylase (GAD) was cloned and overexpressed in E. coli BL21 (DE3) using the pET26b (+) expression vector. Recombinant GAD was purified through a Ni-NTA column and the size was estimated to be 53 kDa by SDS-PAGE. Maximum GAD activity was observed at pH 4.5 and 55℃ and the activity was dependent on pyridoxal 5`-phosphate. The K<sub>m</sub> and V<sub>max</sub> values of GAD were 3.26 ± 0.21 mM and 0.0120 ± 0.0001 mM/min, respectively, when MSG was used as a substrate. Enterococcus avium M5 secretes a lot of GABA when grown on MRS with MSG, and the strain is useful for the production of fermented foods containing a high amount of GABA.
Properties of Kimchi Fermented with GABA-Producing Lactic Acid Bacteria as a Starter
( Kang Wook Lee ),( Jae Min Shim ),( Zhuang Yao ),( Jeong A Kim ),( Jeong Hwan Kim ) 한국미생물생명공학회(구 한국산업미생물학회) 2018 Journal of microbiology and biotechnology Vol.28 No.4
Kimchi (a traditional Korean fermented vegetable) was prepared with a starter, Lactobacillus zymae GU240 producing γ-aminobutyric acid (GABA), and one precursor of GABA (glutamic acid, glutamic acid monosodium salt (MSG), or kelp extract). L. zymae GU240, an isolate from kimchi, can grow at 7% NaCl and low temperature. Five different kimchi samples were fermented for 20 weeks at -1°C. Kimchi with starter alone could not produce GABA. The GABA content was highest in kimchi with co-inoculation of the starter and MSG (1% (w/w)). Kimchi co-inoculated with the starter and kelp extract powder (3% (w/w)) had the second highest GABA content. Addition of glutamic acid powder (1% (w/w)) caused a reduction in the pH level of kimchi and growth inhibition of lactic acid bacteria and yeasts. Kimchi samples with MSG or kelp extract showed improvement of sensory evaluation scores. The results demonstrate the possibility to produce kimchi with improved functionality and taste by using L. zymae GU240 as a starter along with a suitable precursor such as MSG or kelp extract.
( Zhuang Yao ),( Xiaoming Liu ),( Jae Min Shim ),( Kang Wook Lee ),( Hyun-jin Kim ),( Jeong Hwan Kim ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.1
Nine bacilli with fibrinolytic activities were isolated from doenjang, a traditional Korean fermented soy food. Among them, RSB34 showed the strongest activity and was identified as Bacillus amyloliquefaciens by 16S rRNA and recA gene sequencing. During growth on LB up to 96 h, RSB34 showed the highest fibrinolytic activity (83.23 mU/μl) at 48 h. Three bands of 23, 27, and 42 kDa in size were observed when the culture supernatant was analyzed by SDSPAGE and 27 and 42 kDa bands by fibrin zymography. The gene encoding the 27 kDa fibrinolytic enzyme AprE34 was cloned by PCR. BLAST analyses confirmed that the gene was a homolog to genes encoding AprE-type proteases. aprE34 was overexpressed in Escherichia coli BL21(DE3) using pET26b(+). Recombinant AprE34 was purified and examined for its properties. The K<sub>m</sub> and V<sub>max</sub> values of recombinant AprE34 were 0.131 ± 0.026 mM and 16.551 ± 0.316 μM/l/min, respectively, when measured using an artificial substrate, Nsuccinyl- ala-ala-pro-phe-p-nitroanilide. aprE34 was overexpressed in B. subtilis WB600 using pHY300PLK. B. subtilis transformants harboring pHYRSB34 (pHY300PLK with aprE34) showed higher fibrinolytic activity than B. amyloliquefaciens RSB34.
Lee, Kang Wook,Shim, Jae Min,Kim, Dong Wook,Yao, Zhuang,Kim, Jeong A.,Kim, Hyun-Jin,Kim, Jeong Hwan Korean Society of Food Science and Technology 2018 Food Science and Biotechnology Vol.27 No.2
Kimchi was prepared with different types of salts: purified salt (PS), solar salt aged for 1 year (SS1), aged for 3 years (SS3), and bamboo salt (BS). Kimchi inoculated with Leuconostoc mesenteroides P30 (starter kimchi), and control kimchi (non-starter kimchi) were prepared, and stored at - $1^{\circ}C$ for 20 weeks. Titratable acidity values increased slowly and reached 0.96-1.01% (pH 3.73-3.83) at 20 weeks. Proportions of coccus-type lactic acid bacteria (LAB) among total LAB were higher in SS kimchi than PS kimchi. Among non-starter kimchi, the proportions were 44.7, 41.6, 29.7, and 32.1% for SS3, SS1, BS, and PS kimchi, respectively, at 2 weeks, and 11.5, 12.8, 6.7, and 5.8%, respectively, at 20 weeks. SS kimchi had much less yeast counts than PS kimchi. Among starter kimchi, yeasts were detected from PS kimchi at 10 weeks but not detected until 18 weeks from SS1 and BS kimchi and 20 weeks from SS3 kimchi.
DNA Shuffling of aprE Genes to Increase Fibrinolytic Activity and Thermostability
Yao, Zhuang,Jeon, Hye Sung,Yoo, Ji Yeon,Kang, Yun Ji,Kim, Min Jae,Kim, Tae Jin,Kim, Jeong Hwan The Korean Society for Microbiology and Biotechnol 2022 Journal of microbiology and biotechnology Vol.32 No.6
Four aprE genes encoding alkaline serine proteases from B. subtilis strains were used as template genes for family gene shuffling. Shuffled genes obtained by DNase I digestion followed by consecutive primerless and regular PCR reactions were ligated with pHY300PLK, an E. coli-Bacillus shuttle vector. The ligation mixture was introduced into B. subtilis WB600 and one transformant (FSM4) showed higher fibrinolytic activity. DNA sequencing confirmed that the shuffled gene (aprEFSM4) consisted of DNA mostly originated from either aprEJS2 or aprE176 in addition to some DNA from either aprE3-5 or aprESJ4. Mature AprEFSM4 (275 amino acids) was different from mature AprEJS2 in 4 amino acids and mature AprE176 in 2 amino acids. aprEFSM4 was overexpressed in E. coli BL21 (DE3) by using pET26b(+) and recombinant AprEFSM4 was purified. The optimal temperature and pH of AprEFSM4 were similar to those of parental enzymes. However, AprEFM4 showed better thermostability and fibrinogen hydrolytic activity than the parental enzymes. The results indicated that DNA shuffling could be used to improve fibrinolytic enzymes from Bacillus sp. for industrial applications.