Effect of the raceway defects on the nonlinear dynamic behavior of rolling bearing

Ziqiang Zhao,Xuebin Yin,Wenzhong Wang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.6

The defects on raceways would aggravate the vibration of bearing and greatly influence the bearing performance, in order to monitor the running state of the bearing and detect the early defect, the characteristics induced by the defect must be explored. This paper establishes a bearing dynamic model to explore the effect of raceway defects on the nonlinear dynamic behavior of rolling element bearing. The interaction between ball and races is modeled based on Hertz theory, while the presence of defects changes the ball-race interaction. The effects of defect size, position and number on bearing dynamic behaviors are investigated with the aid of phase trajectories, shaft center orbits, FFT spectra, etc. The results indicate that the defects can make the motion of the system more complicated and induce vibration at some characteristic frequencies, which can be used to recognize the bearing failure at early stage. The proposed research provides useful information for the design and status monitoring of mechanical systems.

Applications of Heavy Ion Irradiation in Photonic Crystal Research

Ziqiang Zhao,Yingmin Liu,Yan Chen,Ding Lan,Yuren Wang 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6

Photonic crystals (PC) have received extensive attention for the photonic band gap (PBG). The polystyrene (PS) particles bottom-up approach is a productive method for photonic crystal manufacture, this kind of photonic crystals having an unique PBG that depends on the particle’s shape, sizes and defects. Heavy ion irradiation is a very useful method to induce defects in PC and change the shapes of the particles to tune the PBG. MeV heavy ion irradiation leads to an anisotropic deformation of the particles from spherical to ellipsoidal, the aspect ratio of which can be precisely controlled by using the ion energy and flux. Sub-micrometer PS particles were deposited on a Cu substrate and were irradiated at 230 K by using heavy ion energy and fluence in the range from 2 to 10 MeV and 1 × 1014 cm−2 to 1 × 1015 cm−2, respectively. Photonic crystals (PC) have received extensive attention for the photonic band gap (PBG). The polystyrene (PS) particles bottom-up approach is a productive method for photonic crystal manufacture, this kind of photonic crystals having an unique PBG that depends on the particle’s shape, sizes and defects. Heavy ion irradiation is a very useful method to induce defects in PC and change the shapes of the particles to tune the PBG. MeV heavy ion irradiation leads to an anisotropic deformation of the particles from spherical to ellipsoidal, the aspect ratio of which can be precisely controlled by using the ion energy and flux. Sub-micrometer PS particles were deposited on a Cu substrate and were irradiated at 230 K by using heavy ion energy and fluence in the range from 2 to 10 MeV and 1 × 1014 cm−2 to 1 × 1015 cm−2, respectively.

Rigid-flexible coupling dynamic modeling and performance analysis of a bioinspired jumping robot with a six-bar leg mechanism

Ziqiang Zhang,Lun Wang,Jinnong Liao,Jing Zhao,Qi Yang 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.8

The rigid-flexible coupling structure of creatures with jumping ability has the advantages of high stiffness and good flexibility, which are of great significance to its research. However, existing research on jumping robots has not demonstrated the effect of multiflexibility links on the jumping performance. In this paper, a Watt-type one degree-of-freedom six-bar mechanism is regarded as research object. For a jumping leg including multiple flexible links and a flexible joint with a floating frame, a rigid-flexible coupling dynamic model is established with a pseudo-rigid-body model being used. On this basis, the effect of structural and installation parameters on the jumping performance is analyzed. Results show that different flexible links have distinct effects on the jumping performance, and properly reducing the stiffness of flexible links can improve the jumping performance. The results of this study provide a design basis for jumping robots with a rigid-flexible coupling structure.

Effects of Trapezoidal Fin Shape on Performance of Negative-capacitance FinFETs

Mengjie Zhao,Weifeng Lü,Ziqiang Xie,Mengxue Guo,Mi Lin 대한전자공학회 2022 Journal of semiconductor technology and science Vol.22 No.5

In this study, a negative-capacitance fin field effect transistor (NC-FinFET) with a varying trapezoidal fin shape is proposed. The effects of varying the width of the top fin on the performance of the trapezoidal NC-FinFET with different ferroelectric layer thicknesses are investigated in detail. Using the technology computer-aided design simulation, it was determined that the trapezoidal NC-FinFET has lower on- and off-state currents and a higher switching current ratio, as well as a higher threshold voltage, than a traditional rectangular NC-FinFET. Thus, the device demonstrates an improved subthreshold swing and drain-induced barrier lowering. Unlike a conventional trapezoidal FinFET, the variations in the parameter performance for an NC-FinFET exhibit non-uniform trends. This study provides a predictive estimation for trapezoidal fin-induced variations in an NC-FinFET at the early design stage.

Effects of epigallocatechin-3-gallate on bovine oocytes matured in vitro

Huang, Ziqiang,Pang, Yunwei,Hao, Haisheng,Du, Weihua,Zhao, Xueming,Zhu, Huabin Asian Australasian Association of Animal Productio 2018 Animal Bioscience Vol.31 No.9

Objective: Epigallocatechin-3-gallate (EGCG) is a major ingredient of catechin polyphenols and is considered one of the most promising bioactive compounds in green tea because of its strong antioxidant properties. However, the protective role of EGCG in bovine oocyte in vitro maturation (IVM) has not been investigated. Therefore, we aimed to study the effects of EGCG on IVM of bovine oocytes. Methods: Bovine oocytes were treated with different concentrations of EGCG (0, 25, 50, 100, and $200{\mu}M$), and the nuclear and cytoplasmic maturation, cumulus cell expansion, intracellular reactive oxygen species (ROS) levels, total antioxidant capacity, the early apoptosis and the developmental competence of in vitro fertilized embryos were measured. The mRNA abundances of antioxidant genes (nuclear factor erythriod-2 related factor 2 [NRF2], superoxide dismutase 1 [SOD1], catalase [CAT], and glutathione peroxidase 4 [GPX4]) in matured bovine oocytes were also quantified. Results: Nuclear maturation which is characterized by first polar body extrusion, and cytoplasmic maturation characterized by peripheral and cortical distribution of cortical granules and homogeneous mitochondrial distribution were significantly improved in the $50{\mu}M$ EGCG-treated group compared with the control group. Adding $50{\mu}M$ EGCG to the maturation medium significantly increased the cumulus cell expansion index and upregulated the mRNA levels of cumulus cell expansion-related genes (hyaluronan synthase 2, tumor necrosis factor alpha induced protein 6, pentraxin 3, and prostaglandin 2). Both the intracellular ROS level and the early apoptotic rate of matured oocytes were significantly decreased in the $50{\mu}M$ EGCG group, and the total antioxidant ability was markedly enhanced. Additionally, both the cleavage and blastocyst rates were significantly higher in the $50{\mu}M$ EGCG-treated oocytes after in vitro fertilization than in the control oocytes. The mRNA abundance of NRF2, SOD1, CAT, and GPX4 were significantly increased in the $50{\mu}M$ EGCG-treated oocytes. Conclusion: In conclusion, $50{\mu}M$ EGCG can improve the bovine oocyte maturation, and the protective role of EGCG may be correlated with its antioxidative property.

Experimental Study of Seismic Damage with Park-Ang Model for Recycled Aggregate Concrete Columns

Yujiang Fan,Ziqiang Guo,Yachao Wang,Pengcheng Zhao,Binshan Yu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.9

By means of the low cycle loading tests on six recycled aggregate concrete (RAC) columns with different proportions, in combination with the Park-Ang two-parameter damage model suitable for ordinary concrete columns and the damage degree Dc of actual structures, the calculated value of cyclic loading coefficient β of recycled aggregate concrete columns was determined. It would be achieved by analyzing the calculated β that the impact of the replacement ratio of recycled aggregate and the content of mixed fibers on β was significantly different. Considering the reinforcement ratio mentioned in paper. Matlab was further employed to fit multivariable linear equation regarding recycled aggregate replacement ratio, mixed fibers contents and reinforcement rate as the basis, so that the computation formula of the cyclic loading coefficient β suitable for recycled aggregate concrete columns was revealed.

Mutants Resistant to LpxC Inhibitors by Rebalancing Cellular Homeostasis

Zeng, Daina,Zhao, Jinshi,Chung, Hak Suk,Guan, Ziqiang,Raetz, Christian R. H.,Zhou, Pei American Society for Biochemistry and Molecular Bi 2013 The Journal of biological chemistry Vol.288 No.8

Modeling, analysis, and experiments of a pause-and-leap jumping robot during takeoff, flight, and landing buffering

Qi Yang,Jing Zhao,Ziqiang Zhang,Bin Chang,Xingkun Liu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.10

Jumping robots can overcome obstacles strongly and are suitable for complex terrain environments. However, the takeoff parameters of most jumping robots, especially pause-and-leap jumping robots, cannot be changed accurately. Moreover, the stability of the flight and landing of these robots needs to be improved. On the basis of observations of the jumping process of a locust, leg mechanisms, including one-degree-of-freedom jumping leg and series buffering leg, are designed. Then, dynamic models for takeoff, flight, and landing buffering are established and combined with Lagrange/Newton-Euler dynamic modeling methods and conservation of momentum moment. For the former, the effects of structural parameters, including position of the driving spring, absolute position of the center of mass, and stiffness coefficient of the driving spring, on takeoff velocity and acceleration can be obtained. The takeoff parameters can also be changed accurately. For the flight phase, the relationship between the relative position of the center of mass and the stability of flight is revealed. For the latter, the effects of two buffering modes on the supporting forces and energy storage capacity are analyzed. On the basis of the parameters determined by the abovementioned modeling method, a prototype is developed, and an experiment is conducted to verify the rationality of the modeling method. Experimental results show that the prototype can acquire accurate takeoff parameters and achieve stable flight and landing buffering. This study provides a useful reference for the design and control of jumping robots.

Nitrogen-Doped High Surface Area Carbon as Efficient Electrode Material for Supercapacitors

Kanjun Sun,Qian Yang,Guohu Zhao,Hui Peng,Guofu Ma,Ziqiang Lei 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.7

Polyaspartic acid-based nitrogen-doped porous carbon (N-PC) has been prepared by one-step activation and carbonization of polyaspartic acid at 800℃ in N2 atmosphere. The morphologies and structures of products are characterized by X-ray diffraction, element analysis, scanning electron microscopy and N2 adsorption–desorption. The characterizations show that the morphologies and structures of the N-PC deeply depend on the additive amount of activating agent. The as-prepared activated carbon possesses irregular surface morphology with high surface area in the range of 1600–1800 m2 g-1. Furthermore, the activated carbon possesses proper amount of micropore and mesopore structures. As an electrode material for supercapacitors, the specific capacitance of N-PC is as high as 265 F g-1 at a current density of 0.5 A g-1, and it also exhibits good cyclability (retains about 93% initial capacitance after 5000 cycles).

A 2-40 Gb/s PAM4/NRZ Dual-mode Wireline Transmitter with 4:1 MUX in 65-nm CMOS

Fangxu Lv,Xuqiang Zheng,Feng Zhao,Jianye Wang,Ziqiang Wang,Shuai Yuan,Yajun He,Chun Zhang,Zhihua Wang 대한전자공학회 2018 Journal of semiconductor technology and science Vol.18 No.2

This paper presents a 2-40 Gb/s dual-mode wireline transmitter supporting the four-level pulse amplitude modulation (PAM4) and non-return-tozero (NRZ) modulation with a multiplexer (MUX)-based two-tap feed-forward equalizer (FFE). An edgeacceleration technique is proposed for the 4:1 MUX to increase the bandwidth. By utilizing a dedicated cascode current source, the output swing can achieve 900 mV with a level deviation of only 0.12% for PAM4. Fabricated in a 65-nm CMOS process, the transmitter consumes 117 mW and 89 mW at 40 Gb/s in PAM4 and NRZ at 1.2 V supply.