SPIRAL WAVE GENERATION IN A DIFFUSIVE PREDATOR-PREY MODEL WITH TWO TIME DELAYS

Wenzhen Gan,Peng Zhu 대한수학회 2015 대한수학회보 Vol.52 No.4

This paper is concerned with the pattern formation of a diffusive predator-prey model with two time delays. Based upon an analysis of Hopf bifurcation, we demonstrate that time delays can induce spatial patterns under some conditions. Moreover, by use of a series of numerical simulations, we show that the type of spatial patterns is the spiral wave. Finally, we demonstrate that the spiral wave is asymptotically stable.

The anti-tumor efficacy of 20(S)-protopanaxadiol, an active metabolite of ginseng, according to fasting on hepatocellular carcinoma

Wenzhen Li,YifanWang,Xinbo Zhou,Xiaohong Pan,Junhong Lu,Hongliu Sun,Zeping Xie,Shayan Chen,Xue Gao 고려인삼학회 2022 Journal of Ginseng Research Vol.46 No.1

Background: 20(S)-protopanaxadiol (20(S)-PPD), one of the main active metabolites of ginseng, performs a broad spectrum of anti-tumor effects. Our aims are to search out new strategies to enhance anti-tumor effects of natural products, including 20(S)-PPD. In recent years, fasting has been shown to be multifunctional on tumor progression. Here, the effects of fasting combined with 20(S)-PPD on hepatocellular carcinoma growth, apoptosis, migration, invasion and cell cycle were explored. Methods: CCK-8 assay, trypan blue dye exclusion test, imagings photographed by HoloMonitorTM M4, transwell assay and flow cytometry assay were performed for functional analyses on cell proliferation, morphology, migration, invasion, apoptosis, necrosis and cell cycle. The expressions of genes on protein levels were tested by western blot. Tumor-bearing mice were used to evaluate the effects of intermittent fasting combined with 20(S)-PPD. Results: We firstly confirmed that fasting-mimicking increased the anti-proliferation effect of 20(S)-PPD in human HepG2 cells in vitro. In fasting-mimicking culturing medium, the apoptosis and necrosis induced by 20(S)-PPD increased and more cells were arrested at G0-G1 phase. Meanwhile, invasion and migration of cells were decreased by down-regulating the expressions of matrix metalloproteinase (MMP)-2 and MMP-9 in fasting-mimicking medium. Furthermore, the in vivo study confirmed that intermittent fasting enhanced the tumor growth inhibition of 20(S)-PPD in H22 tumor-bearing mice without obvious side effects. Conclusion: Fasting significantly sensitized HCC cells to 20(S)-PPD in vivo and in vitro. These data indicated that dietary restriction can be one of the potential strategies of chinese medicine or its active metabolites against hepatocellular carcinoma.

Study on cracks and process improvement for case hardened gear shaft straightening

Wenzhen Ma,Hongyao Shen,Guanhua Xu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.6

Deformation of the gear shaft in transmission is inevitable after case hardened heat treatment. Straightening is the normal way to ensure the straightness requirement. During the straightening process, cracks often appear and result in scrapped parts. Based on the situation of high rejection rate of straightening crack of the internal input shaft of a dual-clutch automobile transmission, this paper makes an in-depth analyses of the pressure straightening process theory, the crack generation mechanism, the working process of the automatic straightening machine and the crack detection system, etc., and establishes the relationship between the ram increment, the total displacement and the crack rate during multi-step progressive straightening, proposes a way to quickly judge the straightening performance of the parts. Finally, after optimizing the pressure position by finite element analysis, optimizing the straightening procedure by adjusting ram increment and adopting vector straightening method, optimizing the parts martial properties by heat treatment improvement, the straightening crack rate of internal input shaft was reduced from 1.95 % to 0.14 %.

High‑frequency response current direct demodulation method for sensorless control of interior permanent magnet synchronous motor drives

Wenzhen Li,Jinglin Liu,Chao Gong 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.5

Sensorless schemes are mainly used in fault-tolerant control of interior permanent magnet synchronous motor (IPMSM) drives. Traditional sensorless methods with injection of high-frequency (HF) carrier signals into the stationary reference frame have a stable performance. However, phase shifts caused by conventional high-pass filters (HPFs) decrease the estimation accuracy. Besides, the demodulation process is usually complicated, which increases the difficulty of application. To solve these problems, this study presents an HF-induced current direct demodulation method. Rotor position angle can be solved from the sampled currents at adjacent moments without demodulation signals. Therefore, the errors related to filters in the rotor position estimation are eliminated. Besides, the efficiency of the demodulation algorithm is improved. Furthermore, an online compensation method for cross-saturation effect is proposed. Experimental results verify that the proposed strategy can obtain an accurate rotor position with good steady-state and dynamic performance.

SPIRAL WAVE GENERATION IN A DIFFUSIVE PREDATOR-PREY MODEL WITH TWO TIME DELAYS

GAN, WENZHEN,ZHU, PENG Korean Mathematical Society 2015 대한수학회보 Vol.52 No.4

This paper is concerned with the pattern formation of a diffusive predator-prey model with two time delays. Based upon an analysis of Hopf bifurcation, we demonstrate that time delays can induce spatial patterns under some conditions. Moreover, by use of a series of numerical simulations, we show that the type of spatial patterns is the spiral wave. Finally, we demonstrate that the spiral wave is asymptotically stable.

Study on Stress and Deformation of Bolt Joints of Shield Tunnel under Static and Seismic Action

Wenjun Zhang,Qi Zhang,Wenzhen Cao 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.8

In this paper, three dimensional numerical models for shield tunnel lining bolted joints, which are suitable for seismic excitation and static pressure of surrounding rocks, are established respectively. The influence of different seismic directions on the stress and deformation characteristics of bolted joints is studied in detail. Based on the existing tests, the numerical model of double segment bolted joint was verified. Then, the mechanical properties of the lining joint with different bolted forms were explored, and the applicability analysis of connecting bolted under seismic excitation and surrounding rock static pressure was improved. The results showed that: Compared with the deformation of the circumferential joint under the earthquake transverse excitation, the deformation of the circumferential joint under the longitudinal earthquake excitation is relatively more significant, and the deformation of the inclined bolted joint is the largest. Under the static pressure of surrounding rocks, the opening of the inclined bolted joint is the smallest, but the dislocation is the largest. The opening of the bent bolted joint is the largest, while the dislocation is the smallest. The stress value of the inclined bolted is the largest, whereas the stress value of the bending bolted is the lowest.

The Changes of Absorption and Catalytic Capacity on Reduced Graphene Oxide After Electron Beam Irradiation

Peng Liu,Wei Qi,Wenzhen An,Longlong Tian,Zhan Li,Xiaolei Chen,Wang-Suo Wu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.3

As is well-known, porous nanomaterials have attracted increasing attention recently, and graphene-related materials (such as porous graphene) have been studied both experimentally and theoretically. Almost all researches are focused on nanoelectronics, supercapacitors, multifunctional membrances, bio-applications or others. Consequently, in order to understand the differences between porous graphene and normal graphene at adsorption and catalytic property, in this experiment, with the removal of metal ion (152Eu(III)) and organic matter (gallic acid) and reduction of 4-nitrophenol (4-NP) by NaBH4 as model reactions, a systematic investigation into the adsorptive performance as well as catalytic activity of graphene with or without electron beam irradiation exposure had been carried out. As the results showed, compared with the reduction of pristine graphene oxidized (R-GO), the reduction of graphene oxidized with electron beam irradiation exposure (100 MGy, about 2 h, radiation graphene oxide (R-RGO)) had many irregular defects caused by lack of atoms; the adsorptive performance of the R-RGO increased for metals but decreased for organic matter. However, the adsorption rate of the R-RGO was lower for metals, but higher for organic matter than that of the R-GO. In addition, the results also showed that the R-RGO had a better catalytic capacity than the R-GO.

Identification and Partial Characterization of an Alanine Aminotransferase Gene CsAlaAT2 in Response to Shade in Tea (Camellia sinensis)

Wang Jinhe,Chen Wenzhen,Li Yuanda,Zhao Xiuxiu,Xiang Qinzheng,Li Min 한국식물학회 2021 Journal of Plant Biology Vol.64 No.1

Alanine contributes to the taste and nutritional quality of tea and is an important member of alanine metabolism catalyzed by alanine aminotransferase (AlaAT, EC 2.6.1.2). However, the molecular mechanism underlying alanine metabolism in tea plants has not been fully elucidated. In this study, an increase in enzyme activity of AlaAT2 was detected in vitro, and the alanine aminotransferase activity was higher level in leaves than that in other tissues of tea plant, while the CsAlaAT2 transcription was high in leaves and root. Using phylogenetic analysis, an alanine aminotransferase gene CsAlaAT2 was identified as a member of group C, which was located in the mitochondrion. Additionally, the molecular mass of CsAlaAT2 protein was found to be approximately 53 kDa by SDS-PAGE and western blotting. The CsAlaAT2 expression level and the alanine content in photosynthetic tissues increased in response to the shade treatment. Furthermore, the involvement of CsAlaAT2 in alanine biosynthesis was confirmed based on transient suppression assays in tea leaves, and the alanine content and CsAlaAT2 transcript level decreased when CsAlaAT2 expression was suppressed in tea leaves. Thus, this study suggests that CsAlaAT2 is essential for the alanine metabolism in tea plants grown and its response to shade.

The detection and diagnosis model for small scale MSLB accident

Wang, Meng,Chen, Wenzhen Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.10

The main steam line break accident is an essential initiating event of the pressurized water reactor. In present work, the fuzzy set theory and the signal-based fault detection method has been used to detect the occurrence and diagnosis of the location and break area for the small scale MSLB. The models are validated by the AP1000 accident simulator based on MAAP5. From the test results it can be seen that the proposed approach has a rapid and proper response on accident detection and location diagnosis. The method proposed to evaluate the break area shows good performances for small scale MSLB with the relative deviation within ±3%.

Manganese-based hollow nanoplatforms for MR imaging-guided cancer therapies

Shuang Liang,Guangfu Liao,Wenzhen Zhu,Li Zhang 한국생체재료학회 2022 생체재료학회지 Vol.26 No.3

Theranostic nanoplatforms integrating diagnostic and therapeutic functions have received considerable attention in the past decade. Among them, hollow manganese (Mn)-based nanoplatforms are superior since they combine the advantages of hollow structures and the intrinsic theranostic features of Mn2+. Specifically, the hollow cavity can encapsulate a variety of small-molecule drugs, such as chemotherapeutic agents, photosensitizers and photothermal agents, for chemotherapy, photodynamic therapy (PDT) and photothermal therapy (PTT), respectively. After degradation in the tumor microenvironment (TME), the released Mn2+ is able to act simultaneously as a magnetic resonance (MR) imaging contrast agent (CA) and as a Fenton-like agent for chemodynamic therapy (CDT). More importantly, synergistic treatment outcomes can be realized by reasonable and optimized design of the hollow nanosystems. This review summarizes various Mn-based hollow nanoplatforms, including hollow MnxOy, hollow matrix-supported MnxOy, hollow Mn-doped nanoparticles, hollow Mn complex-based nanoparticles, hollow Mn-cobalt (Co)-based nanoparticles, and hollow Mn-iron (Fe)-based nanoparticles, for MR imaging-guided cancer therapies. Finally, we discuss the potential obstacles and perspectives of these hollow Mn-based nanotheranostics for translational applications. Graphical AbstractMn-based hollow nanoplatforms such as hollow MnxOy nanoparticles, hollow matrix-supported MnxOy nanoparticles, Mn-doped hollow nanoparticles, Mn complex-based hollow nanoparticles, hollow Mn-Cobased nanoparticles and hollow Mn-Fe-based nanoparticles show great promise in cancer theranostics.