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Kun Wen,Li Han,Zhi-ting Zhou,Zhen-nan Fan,Yong Liao,Jun Wang,Zhang Sun,Bing Yao,Bide Zhang 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.3
To obtain more precise and rational calculation details of the loss and heat of a damper winding in a tubular hydro-generator, this study develops a three-dimensional, fi nite-element, electromagnetic-temperature fi eld close-coupling model of the damper winding. On the basis of multi-physical fi eld coupled theory, the model fully considers the temperature eff ects of the damper winding resistivities and heat conductivities, and the eddy current loss in the end region of the damper winding. The model was verifi ed by direct tests of the damper winding temperature. Unlike the conventional weak-coupling model, the proposed close-coupling model fully captures the interaction between the electromagnetic and temperature fi elds. Therefore, of the model more accurately and reasonably calculates the loss and heat of the damper winding than the conventional model. The proposed calculation model can properly assess the loss and heat of damper windings in large hydro-generators, which is helpful for improving the design standards of hydro-generators.
Zhi-ting Zhou,Zhen-nan Fan,Jian-fu Li,Kun Wen,Bide Zhang,Tao Wang,Yan-kun Xia,Zhang Sun,Bing Yao 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.6
A field-circuit coupling model of a typical faulty generator is established to correct through-bolt end-region overheating and breakdown failure in a tubular hydro-generator. Using the model, eddy current loss and electromagnetic forces on through bolts under normal and failure conditions are analyzed and compared and the natural frequency of a through bolt is determined. Based on the analysis results, the causative mechanism of failure is revealed and targeted improvement design measures are proposed. The numerical results are found to be consistent with the actual fault characteristics, validating the design measure improvements. The results are useful in improving the design and manufacturing standards and enhancing the operational reliability of large tubular hydrogenerators.
Zhou, Zhi-ting,Fan, Zhen-nan,Li, Jian-fu,Wen, Kun,Zhang, Bide,Wang, Tao,Xia, Yan-kun,Sun, Zhang,Yao, Bing The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.6
A field-circuit coupling model of a typical faulty generator is established to correct through-bolt end-region overheating and breakdown failure in a tubular hydro-generator. Using the model, eddy current loss and electromagnetic forces on through bolts under normal and failure conditions are analyzed and compared and the natural frequency of a through bolt is determined. Based on the analysis results, the causative mechanism of failure is revealed and targeted improvement design measures are proposed. The numerical results are found to be consistent with the actual fault characteristics, validating the design measure improvements. The results are useful in improving the design and manufacturing standards and enhancing the operational reliability of large tubular hydro-generators.
Xiao-ming Sun,Fu-kun Shi,Ming-qun Zhu,Jia-xu Ding,Lin-sen He,Zhi-hu Li,Tong Zhang,Cheng-yu Miao 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.1
In order to study the damage mechanism of surrounding rocks under water-rock coupling, an experimental study on the microscopic law of water absorption and mechanics of sandy mudstone was carried out in the sandy mudstone stratum of Wanfu coal mine in Shandong, China. The results indicate that the strength of sandy mudstone exhibits three stages of relative softening, rapid softening, and decelerated softening. The speed of water molecules entering the microscopic pore structure was analyzed based on the percentage of water molecules in the pore structure. The acoustic emission energy release process is divided into energy accumulation stage, stable release stage and intense release stage. With the increase of water content saturation, (Spectral width of the multifractal spectrum) tends to decrease and the distribution of events is gradually uniform. The action of water gradually expands and penetrates the cracks and pores inside the sandy mudstone, which makes f (Frequency of occurrence of the signal) change from negative to positive values.
Zhen-nan Fan,Zhi-ting Zhou,Jian-fu Li,Kun Wen,Jun Wang,Zhang Sun,Tao Wang,Bing Yao 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.3
A generator-grid coupling calculation model is established to study the leading-phase operational capability of a 770 MW jumbo hydro-generator in a Chinese ultra-mega hydropower station. The static and dynamic stability of the generator are analyzed and calculated to obtain stability limits under leading-phase operating conditions. Three-dimensional (3D) time-varying nonlinear moving electromagnetic and temperature field models of the generator end-region are also established and used to determine the magnetic field, loss, and temperature of the end-region under the leading-phase operating condition. The simulation results agree with data measured from the actual 770 MW hydro-generator. This paper provides reliable reference data for the leading-phase operation of a jumbo hydro-generator, which will help to improve in the design and manufacture of future hydro-generators.
Fan, Zhen-nan,Zhou, Zhi-ting,Li, Jian-fu,Wen, Kun,Wang, Jun,Sun, Zhang,Wang, Tao,Yao, Bing The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.3
A generator-grid coupling calculation model is established to study the leading-phase operational capability of a 770 MW jumbo hydro-generator in a Chinese ultra-mega hydropower station. The static and dynamic stability of the generator are analyzed and calculated to obtain stability limits under leading-phase operating conditions. Three-dimensional (3D) time-varying nonlinear moving electromagnetic and temperature field models of the generator end-region are also established and used to determine the magnetic field, loss, and temperature of the end-region under the leading-phase operating condition. The simulation results agree with data measured from the actual 770 MW hydro-generator. This paper provides reliable reference data for the leading-phase operation of a jumbo hydro-generator, which will help to improve in the design and manufacture of future hydro-generators.
Jun-wei Gao,Zhi-hai Peng,Xiao-yu Li,Bo Sun,Yan-kun Guo,Gao-lin Liu 대한약학회 2011 Archives of Pharmacal Research Vol.34 No.1
In this study, we determined the pharmacokinetics of mycophenolic acid (MPA) and its metabolites mycophenolic acid glucuronide (MPAG) and acyl glucuronide (AcMPAG) in rat plasma and bile, using a newly developed HPLC method. Protein precipitation and liquid-liquid extraction were employed in sample preparation of plasma and bile, respectively. The HPLC methods included a gradient elution consisting of acetonitrile and phosphate buffer at a flow rate of 1.2 mL/min, with UV detection at 254 nm. The HPLC method was found to be sensitive and linear (r^2 ≥ 0.9991, 1.0-128.0 and 0.25-32.0 mg/L for MPA; 1.0-128.0 and 0.5-64.0 mg/L for MPAG; 0.25-32.0 and 1.0-128.0 mg/L for AcMPAG in rat plasma and bile, respectively), precise (both the intra- and inter-day variability were ≤ 6.8%), and accurate (both the intra- and inter-day accuracy were between 92.2% and 105.4%). The average extraction efficiencies for MPA, MPAG and AcMPAG were 85.3%, 100.1%, and 94.7% in plasma, and 88.0%, 67.3%, and 68.3% in bile, respectively. The method was successfully employed for pharmacokinetic studies in plasma and bile after oral administration of mycophenolate mofetil (prodrug of MPA) in rats.
Hong-Qi Yang,Wen-Cong Zhao,Wei-Min Yang,Yong-Li Li,Zhi-Kun Sun,Shuai Chen,Wei Li,Jian-Jun Ma 대한신경과학회 2016 Journal of Clinical Neurology Vol.12 No.3
Background and PurposezzAcute disseminated encephalomyelitis (ADEM) is an infammatory demyelinating disorder that predominantly afects children. Previous studies have mostly involved children in Western developed countries. MethodszzTis study retrospectively reviewed the clinical profles of ADEM in adult Chinese patients. ResultszzADEM occurred during summer and autumn in about two-thirds of the 42 included patients. Prior infection was found in fve patients and no preimmunization was recorded. Te most frequent clinical presentations were alterations in consciousness (79%) and behavior changes (69%), followed by motor defcits (64%) and fever (50%). About one-quarter (26%) of the patients showed positive results for oligoclonal bands, and about half of them exhibited increases in the IgG index and 24-hour IgG synthesis rate. Magnetic resonance imaging showed white- and gray-matter lesions in 83% and 23% of the patients, respectively. Steroids were the main treatment, and full recovery occurred in 62% of the patients, with residual focal neurological defcits recorded in a few patients. Afer a mean follow-up period of 3.4 years, two patients exhibited recurrence and one patient exhibited a multiphasic course. One patient was diagnosed with multiple sclerosis (MS). ConclusionszzWith the exception of the seasonal distribution pattern and prior vaccine rate, the clinical profles of ADEM in adult Chinese patients are similar to those in pediatric populations. No specifc markers are available for distinguishing ADEM from MS at the initial presentation. Careful clinical evaluations, cerebrospinal fuid measurements, and neuroradiological examinations with long-term follow-up will aid the correct diagnosis of ADEM.