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Cheng Feng,Li Jianbo,Ding Zhixin,Lin Gao 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.3
The dynamic structural responses are sensitive to the time-frequency content of seismic waves, and seismic input motions in time-history analysis are usually required to be compatible with design response spectra according to nuclear codes. In order to generate spectra-compatible input motions while maintaining the intrinsic non-stationarity of seismic waves, an improved time-domain approach is proposed in this paper. To maintain the nonstationary characteristics of the given seismic waves, a new time-frequency envelope function is constructed using the Hilbert amplitude spectrum. Based on the intrinsic mode functions (IMFs) obtained from given seismic waves through variational mode decomposition, a new corrective time history is constructed to locally modify the given seismic waves. The proposed corrective time history and time-frequency envelope function are unique for each earthquake records as they are extracted from the given seismic waves. In addition, a dimension reduction iterative technique is presented herein to simultaneously superimpose corrective time histories of all the damping ratios at a specific frequency in the time domain according to optimal weights, which are found by the genetic algorithm (GA). Examples are presented to show the capability of the proposed approach in generating spectra-compatible time histories, especially in maintaining the nonstationary characteristics of seismic records. And numerical results reveal that the modified time histories generated by the proposed method can obtain similar dynamic behaviors of AP1000 nuclear power plant with the natural seismic records. Thus, the proposed method can be efficiently used in the design practices
“Let’s Kill All the Lawyers” : Legal Illegalities in The Merchant of Venice
Cheng Feng 행정언어와 질적연구학회 2014 행정언어와 질적연구 Vol.5 No.1
Based on the assumption that Shakespeare is versed in the legal codes in his time, this paper intends to locate all the legal inaccuracies in The Merchant of Venice, a play known for its legal theme, and argues that these aberrations are consciously committed. Shakespeare deliberately creates a court scene that flouts important legal principles so as to reflect inequalities in the power relationships between various subcultures; law, the supposed embodiment of justice, is subtly tilted in favor of the more privileged groups and the more established discourses.
Li Chengfeng,Lyu Qishen,Li Zheng,Yang Shuliang,Sun Yong,Tang Xing,Zeng Xianhai,Lin Lu 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.9
The hydrogenation of biomass-based furan compounds is an important step for the catalytic valorization of biobased chemicals. In this work, Ru-based catalysts supported on different supports, such as HY, MgO and Amberlyst-15, were prepared and estimated for the hydrogenation of dimethyl 2,5-furandicarboxylate (FDMC). Among them, Ru/HY provided a desirable yield of 99.4% for tetrahydrofuran-2,5-dicarboxylic acid dimethyl ester (THFDMC) under 90 °C and 3 MPa H2. Based on catalyst characterization, Ru/HY could offer more surface Ru0 species and carbon radical intermediates than other catalysts, which could largely favor the activation of hydrogen and then promote the hydrogenation of FDMC over Ru/HY.
Tribological performance of some organic fluorine-containing compounds as lubricants
Weimin Liu,Chengfeng Ye,Qunji Xue 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.2002 No.10
The friction and wear behaviors of fluorine-containing compounds such as perfluoropolyethers (PFPE), phosphazenes (X-1P), ionic liquids as lubricants for steel/seel, steel/ceramic, ceramic/ceramic were investigated using a SRV tester and a one-way reciprocating friction tester both in ball-on-disc configuration. It was found that the three fluorine-containing lubricants could reduce friction coefficient and wear volume effectively. The effectiveness of the three lubricants in reducing wear volume could be ranked as ionic liquids>X-1P>PFPE. Tests also showed that aryloxyphosphazene with polar substituent as a lubricant of steel/steel pair gave low wear, while aryloxyphosphazene with nonpolar group on the phenyl pendant led to high wear. The morphology and the tribo-chemical reaction of the worn surfaces were analyzed with a scanning electron microscope (SEM) and X-ray photoelectron spectroscope (XPS). XPS analyses illustrated the formation of iron fluoride in steel/steel system with the lubrication of both phosphazenes and ionic liquids.
A fast numerical method for solving a regularized problem associated with obstacle problems
DaMing Yuan,Xi Li,ChengFeng Lei 대한수학회 2012 대한수학회지 Vol.49 No.5
Kirsi Majava and Xue-Cheng Tai [12] proposed a modified level set method for solving a free boundary problem associated with unilateral obstacle problems. The proximal bundle method and gradient method were applied to solve the nonsmooth minimization problems and the regularized problem, respectively. In this paper, we extend this approach to solve the bilateral obstacle problems and employ Rung-Kutta method to solve the initial value problem derived from the regularized problem. Numerical experiments are presented to verify the efficiency of the methods.
Yang Leilei,Fang Chengfeng,Song Caifang,Zhang Yaya,Zhang Ruili,Zhou Shenkang 한국조직공학과 재생의학회 2023 조직공학과 재생의학 Vol.20 No.5
BACKGROUND: Radiation enteritis (RE) is a common complication of abdominal or pelvic radiotherapy, which when severe, could be life-threatening. Currently, there are no effective treatments. Studies have shown that mesenchymal stem cells (MSCs)-derived exosomes (MSC-exos) exhibit promising therapeutic effects in inflammatory diseases. However, the specific role of MSC-exos in RE and the regulatory mechanisms remain elusive. METHODS: In vivo assay was carried out by injecting MSC-exos into the total abdominal irradiation (TAI)-induced RE mouse model. For in vitro assay, Lgr5-positive intestinal epithelial stem cells (Lgr5? IESC) were extracted from mice, followed by irradiation along with MSC-exos treatment. HE staining was performed to measure histopathological changes. mRNA expression of inflammatory factors TNF-a and IL-6 and stem cell markers LGR5, and OCT4 were quantified by RT-qPCR. EdU and TUNEL staining was performed to estimate cell proliferation and apoptosis. MiR-195 expression in TAI mice and radiation-induced Lgr5? IESC was tested. RESULTS: We found that the injection of MSC-exos inhibited inflammatory reaction, increased stem cell marker expression, and maintained intestinal epithelial integrity in TAI mice. Furthermore, MSC-exos treatment increased the proliferation and simultaneously suppressed apoptosis in radiation-stimulated Lgr5? IESC. MiR-195 expression increased by radiation exposure was decreased by MSC-exos therapy. MiR-195 overexpression facilitated the progress of RE by counteracting the effect of MSC-exos. Mechanistically, the Akt and Wnt/b-catenin pathways inhibited by MSC-exos were activated by miR-195 upregulation. CONCLUSION: MSC-Exos are effective in treating RE and are essential for the proliferation and differentiation of Lgr5? IESCs. Moreover, MSC-exos mediates its function by regulating miR-195 Akt b-catenin pathways.
Kai Lv,Chengwu Shi,Zhengguo Zhang,Chengfeng Ma,Qi Wang 한국물리학회 2018 Current Applied Physics Vol.18 No.6
In this work, PbICl precursor solution in N,N-dimethylformamide was successfully applied to deposit PbS quantum-dots on TiO2 nanorod arrays by successive ionic layer adsorption and reaction method (SILAR). The influence of PbI2, PbBr2, PbICl precursor solution on the morphology, crystal size and optical absorption of PbS quantum-dots was investigated and the photovoltaic performance of the corresponding solid-state PbS quantumdot sensitized TiO2 nanorod array solar cells with spiro-OMeTAD was evaluated. The average crystal sizes of PbS quantum-dots were 9.0 nm of PbI2, 8.6 nm of PbBr2 and 8.4 nm of PbICl and the photoelectric conversion efficiency of the corresponding solar cells achieved 2.63%, 3.00%, 3.45%. The result revealed that PbICl precursor solution was superior to PbBr2 and PbI2.
A FAST NUMERICAL METHOD FOR SOLVING A REGULARIZED PROBLEM ASSOCIATED WITH OBSTACLE PROBLEMS
Yuan, Daming,Li, Xi,Lei, Chengfeng Korean Mathematical Society 2012 대한수학회지 Vol.49 No.5
Kirsi Majava and Xue-Cheng Tai [12] proposed a modified level set method for solving a free boundary problem associated with unilateral obstacle problems. The proximal bundle method and gradient method were applied to solve the nonsmooth minimization problems and the regularized problem, respectively. In this paper, we extend this approach to solve the bilateral obstacle problems and employ Rung-Kutta method to solve the initial value problem derived from the regularized problem. Numerical experiments are presented to verify the efficiency of the methods.
Bai, Jiahai,Piao, Jiasi,Gao, Jie,He, Jing,Du, Qingyang,Li, Chengfeng The Korean Ceramic Society 2019 한국세라믹학회지 Vol.56 No.4
Porous alumina ceramics with addition of 0, 5, 10, 15, and 20 wt% Al(H<sub>2</sub>PO<sub>4</sub>)<sub>3</sub> were sintered at 1300, 1350, and 1400℃. The effects of the Al(H<sub>2</sub>PO<sub>4</sub>)<sub>3</sub> addition on crystal phases, water absorption, open porosity, pore size distribution, microstructures, and flexural strength were studied extensively. The experimental results revealed that only characteristic peaks of corundum were indexed in the XRD patterns of the as-prepared porous ceramics. The water absorption and open porosity of the porous Al<sub>2</sub>O<sub>3</sub> ceramics increased remarkably with an increase in Al(H<sub>2</sub>PO<sub>4</sub>)<sub>3</sub> addition. The flexural strength first increased to a maximum value when 5 wt% Al(H<sub>2</sub>PO<sub>4</sub>)<sub>3</sub> was added and then decreased as additional Al(H<sub>2</sub>PO<sub>4</sub>)<sub>3</sub> was further added. SEM images showed that the average Al<sub>2</sub>O<sub>3</sub> grain size in the porous ceramics changed in an opposite way as the flexural strength. The porous Al<sub>2</sub>O<sub>3</sub> ceramics with 10 wt% Al(H<sub>2</sub>PO<sub>4</sub>)<sub>3</sub> addition exhibited comparable flexural strength to the ceramics without Al(H<sub>2</sub>PO<sub>4</sub>)<sub>3</sub> addition, although the latter had much higher porosity.