Frequency capture characteristics of vibration system with two degrees of freedom

Sun Zhijun,Hou Li,Wei Yongqiao,Li Bo,Jia Fenglan 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.7

In this study, the dynamical model of the vibration of the wind power system was established according to the Lagrange’s principle forinvestigating the phenomenon of frequency capture. The system response of the vibration of wind power device in the horizontal andvertical directions of tower was analyzed by numerical simulation. At the same time, the paper analyzed the characteristics of the vibrationmodel comparing with the traditional model. Then the conditions of frequency capture were studied through the analysis of mathematicalmodel. In particular, the effects that five key parameters had on the frequency capture characteristics were analyzed. Finally, theresearch reveal that reducing the eccentric mass and eccentricity of the blade, increasing the support stiffness and displacement dampingcoefficient, and increasing the torque of the input shaft can reduce vibration and avoid the phenomenon of frequency capture. The simulationresults provide the theory basis for the design and installation of wind power device.

섬 관광의 지속가능성에 관한 연구

손지군(Zhijun Sun),한주형(Ju Hyoung Han) 융합관광콘텐츠학회 2024 융합관광콘텐츠연구 (JCTC) Vol.10 No.1

Simulation study of new directional drilling PDC bit used in coal mine

Rongjun Sun,Pei Ju,Zhijun Shi 한국자원공학회 2017 Geosystem engineering Vol.20 No.3

During directional drilling, when drilling in hard and multi-interbedded formation, the ordinary flat-bottomed PDC bit wears seriously, in order to solve this problem, a new type of directional drilling PDC bit (straight angle drag PDC bit) is developed, and numerical simulation method is used to analyze the working characteristics of straight angle drag PDC bit. Simulation results show that, comparing with the ordinary flat-bottomed PDC bit, axial force needed by straight angle drag PDC bit reduces by up to 36%, and rock breaking efficiency increases nearly 50%. Also, Φ96 mm straight angle drag PDC bit is produced and field test is carried out; field test results show that: comparing with flat-bottomed PDC bit, bit life expectancy of straight angle drag PDC bit increases more than three times, and rock breaking efficiency increases about two times. So, when drilling in hard and multi-interbedded formation in the process of directional drilling, straight angle drag PDC bit helps to improve bit life and rock breaking efficiency and finally reduces drilling cost.

An efficient and Scalable Metro-Ethernet Architecture

Xiaocui Sun,Zhijun Wang 보안공학연구지원센터(IJSIP) 2010 International Journal of Signal Processing, Image Vol.3 No.4

Extreme Liquidity Risk and the Cross‐Section of Expected Returns: Evidence from China

Hu Zhijun,Sun Ping‐Wen 한국증권학회 2023 Asia-Pacific Journal of Financial Studies Vol.52 No.2

In this study, we investigate whether extreme liquidity risk is priced in the China A-shares market. We find that the market extreme liquidity risk significantly and negatively predicts market returns up to 9 months. In addition, the extreme liquidity risk beta of individual stocks commands a positive monthly premium of 0.75%. Moreover, our findings show that the extreme liquidity risk beta can subsume the tail risk beta in predicting stock returns. Furthermore, our findings show that both the potential selling pressures caused by insiders and by institutional investors significantly and positively influence an individual stock’s extreme liquidity risk beta. We also find that the potential selling pressure component of the extreme liquidity risk beta significantly and positively predicts stock returns. Taken together, our evidence demonstrates that a stock’s extreme liquidity risk beta provides a channel through which the stock’s potential selling pressure caused by both insiders and institutional investors influences its expected return in the China A-shares market.

Changes in microbial population and chemical composition of corn stover during field exposure and effects on silage fermentation and in vitro digestibility

Lin Sun,Zhijun Wang,Ge Gentu,Yushan Jia,Meiling Hou,Yimin Cai 아세아·태평양축산학회 2019 Animal Bioscience Vol.32 No.6

Objective: To effectively use corn stover resources as animal feed, the changes in microbial population and chemical composition of corn stover during field exposure, and their silage fermentation and in vitro digestibility were studied. Methods: Corn cultivars (Jintian, Jinnuo, and Xianyu) stovers from 4 random sections of the field were harvested at the preliminary dough stage of maturity on September 2, 2015. The corn stover exposed in the field for 0, 7, 15, 30, 60, 90, and 180 d, and their silages at 60 d of ensiling were used for the analysis of microbial population, chemical composition, fermentation quality, and in vitro digestibility. Data were analyzed with a completely randomized 3×6 [corn stover cultivar (C)×exposure d (D)] factorial treatment design. Analysis of variance was performed using SAS ver. 9.0 software (SAS Institute Inc., Cary, NC, USA). Results: Aerobic bacteria were dominant population in fresh corn stover. After ensiling, the lactic acid bacteria (LAB) became the dominant bacteria, while other microbes decreased or dropped below the detection level. The crude protein (CP) and water-soluble carbohydrate (WSC) for fresh stover were 6.74% to 9.51% and 11.75% to 13.21% on a dry matter basis, respectively. After exposure, the CP and WSC contents decreased greatly. Fresh stover had a relatively low dry matter while high WSC content and LAB counts, producing silage of good quality, but the dry stover did not. Silage fermentation inhibited nutrient loss and improved the fermentation quality and in vitro digestibility. Conclusion: The results confirm that fresh corn stover has good ensiling characteristics and that it can produce silage of good quality.

Inhibition of L-type Ca²⁺ current by ginsenoside Rd in rat ventricular myocytes

Lu, Cheng,Sun, Zhijun,Wang, Line The Korean Society of Ginseng 2015 Journal of Ginseng Research Vol.39 No.2

Background: Ginsenoside Rd (GSRd), one of the most abundant ingredients of Panax ginseng, protects the heart via multiple mechanisms including the inhibition of $Ca^{2+}$ influx.We intended to explore the effects of GSRd on L-type $Ca^{2+}$ current ($I_{Ca,L}$) and define the mechanism of the suppression of $I_{Ca,L}$ by GSRd. Methods: Perforated-patch recording and whole-cell voltage clamp techniques were applied in isolated rat ventricular myocytes. Results: (1) GSRd reduced $I_{Ca,L}$ peak amplitude in a concentration-dependent manner [half-maximal inhibitory concentration $(IC_{50})=32.4{\pm}7.1{\mu}mol/L$] and up-shifted the current-voltage (I-V) curve. (2) GSRd ($30{\mu}mol/L$) significantly changed the steady-state activation curve of $I_{Ca,L}$ ($V_{0.5}:-19.12{\pm}0.68$ vs. $-6.26{\pm}0.38mV$; n = 5, p < 0.05) and slowed down the recovery of $I_{Ca,L}$ from inactivation [the time content (${\zeta}$) from 91 ms to 136 ms, n = 5, p < 0.01]. (3) A more significant inhibitive effect of GSRd ($100{\mu}mol/L$) was identified in perforated-patch recording when compared with whole-cell recording [$65.7{\pm}3.2%$ (n = 10) vs. $31.4{\pm}5.2%$ (n = 5), p < 0.01]. (4) Pertussis toxin ($G_i$ protein inhibitor) completely abolished the $I_{Ca,L}$ inhibition induced by GSRd. There was a significant difference in inhibition potency between the two cyclic adenosine monophosphate elevating agents (isoprenaline and forskolin) prestimulation [$55{\pm}7.8%$ (n = 5) vs. $17.2{\pm}3.5%$ (n = 5), p < 0.01]. (5) 1H-[1,2,4]Oxadiazolo[4,3-a]-quinoxalin-1-one (a guanylate cyclase inhibitor) and N-acetyl-$\small{L}$-cysteine (a nitric oxide scavenger) partly recovered the $I_{Ca,L}$ inhibition induced by GSRd. (6) Phorbol-12-myristate-13-acetate (a protein kinase C activator) and GF109203X (a protein kinase C inhibitor) did not contribute to the inhibition of GSRd. Conclusion: These findings suggest that GSRd could inhibit $I_{Ca,L}$ through pertussis toxin-sensitive G protein ($G_i$) and a nitric oxide-cyclic guanosine monophosphate-dependent mechanism.

Inhibition of L-type Ca<SUP>2+</SUP> current by ginsenoside Rd in rat ventricular myocytes

Cheng Lu,Zhijun Sun,Line Wang 고려인삼학회 2015 Journal of Ginseng Research Vol.39 No.2

Background: Ginsenoside Rd (GSRd), one of the most abundant ingredients of Panax ginseng, protects the heart via multiple mechanisms including the inhibition of Ca<SUP>2+</SUP> influx. We intended to explore the effects of GSRd on L-type Ca2+ current (ICa,L) and define the mechanism of the suppression of ICa,L by GSRd. Methods: Perforated-patch recording and whole-cell voltage clamp techniques were applied in isolated rat ventricular myocytes. Results: (1) GSRd reduced ICa,L peak amplitude in a concentration-dependent manner [half-maximal inhibitory concentration (IC50) = 32.4± 7.1 μmol/L] and up-shifted the currente-voltage (I-V) curve. (2) GSRd (30 μmol/L) significantly changed the steady-state activation curve of ICa,L (V0.5: -19.12± 0.68 vs. -16.26 ± 0.38 mV; n = 5, p < 0.05) and slowed down the recovery of ICa,L from inactivation [the time content (ζ) from 91 ms to 136 ms, n = 5, p < 0.01]. (3) A more significant inhibitive effect of GSRd (100 μmol/L) was identified in perforated-patch recording when compared with whole-cell recording [65.7 ±3.2% (n = 10) vs. 31.4 ± 5.2% (n=5), p < 0.01]. (4) Pertussis toxin (Gi protein inhibitor) completely abolished the ICa,L inhibition induced by GSRd. There was a significant difference in inhibition potency between the two cyclic adenosine monophosphate elevating agents (isoprenaline and forskolin) prestimulation [55± 7.8% (n = 5) vs. 17.2 ± 3.5% (n= 5), p < 0.01]. (5) 1H-[1,2,4]Oxadiazolo[4,3-a]-quinoxalin-1-one (a guanylate cyclase inhibitor) and N-acetyl-L-cysteine (a nitric oxide scavenger) partly recovered the ICa,L inhibition induced by GSRd. (6) Phorbol-12-myristate-13-acetate (a protein kinase Cactivator) and GF109203X (a protein kinase C inhibitor) did not contribute to the inhibition of GSRd. Conclusion: These findings suggest that GSRd could inhibit ICa,L through pertussis toxin-sensitive G protein (Gi) and a nitric oxideecyclic guanosine monophosphate-dependent mechanism.

Microstructure and Electromagnetic Properties of Y3+ Substituted Mg-Mn Nanocrystalline Ferrites Via Hydrothermal Procedure

Renxin Xu,Huan Yang,Huajun Sun,Jing Zhou,Zhijun Yue,Xinhua Gao 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.2

Mg0.2Mn0.8YxFe2-xO4 (x = 0.000, 0.025, 0.050 and 0.075) nanocrystalline is synthesized via hydrothermal technique. Single cubic spinel phase is confirmed by XRD and the formation of Mg0.2Mn0.8YxFe2-xO4 is verified by EDS. The average size of the nanoferrites is around 80 nm, which is examined by TEM image. Y3+ substituted Mg-Mn nanoferrites exhibit low saturation magnetization (Ms) and coercivity (Hc). Especially, the nanoferrites with x = 0.075 show the lowest Ms and Hc of 46.96 emu/g and 12.04 Oe, respectively. The ferrite composites present that the resistivity and the magnetic loss are less than 4.5 x 10 7 Ω · cm and 0.7 in the range of 2–18 GHz, respectively. The low coercivity and high resistivity indicate that the addition of Y3+ contributes to the synthesis of the excellent soft magnetic materials.

Fuzzy Control Strategy for Course Correction of Omnidirectional Mobile Robot

Niu Zijie,Lu Qiang,Cui Yonjie,Sun Zhijun 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.9

Omnidirectional mobile robots (OMRs) based on the Mecanum wheel, often slide during driving and cause the actual course to deviate from the set heading. To improve the OMR course accuracy, we propose a fuzzyPI control algorithm that modifies the OMR course in real time, by analyzing the omnidirectional movement of the Mecanum wheel and the kinematic model of the OMR. fuzzification, fuzzy reasoning, and defuzzification, the robot’s heading is corrected in real time. Analysis of the yaw error of the robots, with and without the fuzzy PI control algorithm, show that the yaw error has been reduced from the original values of −2.5-0◦ and −10.5-0◦ down to −0.6-0.6◦ and −1-0◦ , when the robot travels a distance of 3.5 m in the longitudinal and transverse directions, respectively. Through experiments, the traditional PI control algorithm and fuzzy PI control algorithm are compared in terms of the robot heading-regulation performance. From the analysis of experimental data, we can see that, when the yaw error of an OMR with the fuzzy PI control algorithm is between 35 and 40◦, the adjustment time is sped up by 1.3 s and 1.2 s and overshoot angle is reduced by 7.7◦ and 4.3◦ , respectively, for longitudinal and transverse movements. Both experimental results show that the fuzzy PI control algorithm has good regulation performance and can achieve good control effects.