http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Zheng Feng Bai,Yu Qiang Liu,Yi Sun 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.2
The effects of clearance on dynamic responses of dual-axis positioning mechanism of a satellite antenna are investigated using a computationalmethodology. Considering clearances in joints, the clearance is defined and the mathematical model of revolute joint withclearance is presented. The normal contact force model and tangential friction model in clearance joint are established using nonlinearcontinuous contact force model and Coulomb friction model, respectively. Then numerical simulation is used to investigate the dynamicresponses of dual-axis positioning mechanism with joint clearance. The results show that clearance has significant effects on dynamicresponses of mechanism, and the investigation of the work can predict the dynamic responses of dual-axis positioning mechanism withclearance preferably, which is the basis of mechanism design, precision analysis and control system design.
Reducing undesirable vibrations of planar linkage mechanism with joint clearance
Zheng Feng Bai,Xin Jiang,Fei Li,Ji Jun Zhao,Yang Zhao 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.2
An optimization design method is presented to reduce the undesirable vibrations caused by clearance for planar linkage mechanism. A clearance joint is defined and considered a contact/impact force constraint. Contact and impact force models for the clearance joint are established using a normal contact force model based on Hertz model with energy loss and a tangential friction model based on modified Coulomb model with dynamic friction coefficient, respectively. In view of the clearance joint, dynamic equations and optimization method for a planar four-bar mechanism are then presented as an application example. The optimization aims to minimize the maximum absolute acceleration peaks of the mechanism by determining the link lengths of the planar linkage mechanism. Finally, the optimization design is solved by a generalized reduced gradient algorithm. Results show evident decrease in vibration peaks of the mechanism and obvious reduction in the contact forces in the clearance joint, which contribute to a good performance of planar linkage mechanism systems.
Effect of Nd Substitution for Mischmetal on Magnetic Properties in (MM,Nd)-Fe-B Ribbons
Zhu-bai Li,Jing-zhao Li,Zhi-yi Xu,Yong-feng Li,Xue-feng Zhang 한국자기학회 2020 Journal of Magnetics Vol.25 No.1
Mischmetal-based permanent magnets of (MM,Nd)12Fe82B6 were prepared by melt-spinning method via varying the relative content of mischmetal and Nd. The coercivity is low, and the squareness of hysteresis loop is poor in MM12Fe82B6 ribbons. The x-ray diffraction pattern, maximum of δm value as well as the temperature dependence of magnetization indicates that the partial substitution of Nd for MM could improve the crystallinity in the mischmetal-based magnets, and both the coercivity and squareness of hysteresis loop increase with Nd substitution for mischmetal. The increase of squareness should be partially attributed to the improvement in the crystallinity of R₂Fe14B crystal phase. For more than 4 at.% Nd substitution the coercivity is not less than that in corresponding (Ce,Nd)-based magnets, and the coercivity of 7.81 kOe and the maximum energy product of 15.41 MGOe were obtained in MM8Nd₄Fe82B6 ribbons. These investigations show that it is reasonable to use the low cost mischmetal to prepare the resource-saving rare-earth magnets, and that optimizing the addition amount of Nd is necessary to improve the crystallinity and enhance the magnetic properties.
Liu Yan-ju,Jiang Jin-gang,Miao Feng-juan,Tao Bai-rui,Zhang Hong-lie 보안공학연구지원센터 2014 International Journal of Grid and Distributed Comp Vol.7 No.5
This paper presents a fuzzy normal estimate for mass point clouds of irregular models in reconstruction. The irregular model is complex object that some part is smooth and some parts are irregular including sharp features. Therefore, we put kNN and curvature of mass point clouds to fuzzy inference system to divide the kind of point clouds and the output of FIS can determine which part of tooth point clouds belong to. For different kinds point clouds, corresponding algorithm is given. Point clouds in the smooth area are estimated normal by PCA directly and ones in other regions of thin or sharp area are estimated by checker and attach points. This method is simpler than those complex methods used on the whole point clouds directly. The experiment results show that much time is saved and surface reconstruction is very fine than PCA and WLOP.
Bai-Ni Guo,Feng Qi 대한수학회 2011 대한수학회지 Vol.48 No.3
A class of functions involving divided differences of the psi and tri-gamma functions and originating from Kershaw's double inequality are proved to be completely monotonic. As applications of these results, the monotonicity and convexity of a function involving the ratio of two gamma functions and originating from the establishment of the best upper and lower bounds in Kershaw's double inequality are derived, two sharp double inequalities involving ratios of double factorials are recovered, the probability integral or error function is estimated, a double inequality for ratio of the volumes of the unit balls in $\mathbb{R}^{n-1}$ and $\mathbb{R}^n$ respectively is deduced, and a symmetrical upper and lower bounds for the gamma function in terms of the psi function is generalized.
Different Regulation of Atrial ANP Release through Neuropeptide Y₂ and Y₄ Receptors
Feng Lian Piao,Kuichang Yuan,Guang Yi Bai,한정희,박우현,김선희 대한의학회 2008 Journal of Korean medical science Vol.23 No.6
Neuropeptide Y (NPY) receptors are present in cardiac membranes. However, its physiological roles in the heart are not clear. The aim of this study was to define the direct effects of pancreatic polypeptide (PP) on atrial dynamics and atrial natriuretic peptide (ANP) release in perfused beating atria. Pancreatic polypeptides, a NPY Y₄ receptor agonist, decreased atrial contractility but was not dose-dependent. The ANP release was stimulated by PP in a dose-dependent manner. GR 23118, a NPY Y₄ receptor agonist, also increased the ANP release and the potency was greater than PP. In contrast, peptide YY (3-36) (PYY), an NPY Y2 receptor agonist, suppressed the release of ANP with positive inotropy. NPY, an agonist for Y1, 2, 5 receptor, did not cause any significant changes. The pretreatment of NPY (18-36), an antagonist for NPY Y₃ receptor, markedly attenuated the stimulation of ANP release by PP but did not affect the suppression of ANP release by PYY. BIIE0246, an antagonist for NPY Y₂ receptor, attenuated the suppression of ANP release by PYY. The responsiveness of atrial contractility to PP or PYY was not affected by either of the antagonists. These results suggest that NPY Y₄ and Y₂ receptor differently regulate the release of atrial ANP.
MONOTONICITY AND LOGARITHMIC CONVEXITY OF THREE FUNCTIONS INVOLVING EXPONENTIAL FUNCTION
Bai-Ni Guo,Ai-Qi Liu,Feng Qi 한국수학교육학회 2008 純粹 및 應用數學 Vol.15 No.4
In this note, an alternative proof and extensions are provided for the following conclusions in [6, Theorem 1 and Theorem 3]: The functions 1 x2 ¡ e¡x (1¡e¡x)2 and 1 t ¡ 1 et¡1 are decreasing in (0;1) and the function t eat¡e(a¡1)t for a 2 R and t 2 (0;1) is logarithmically concave.
TWO NEW PROOFS OF THE COMPLETE MONOTONICITY OF A FUNCTION INVOLVING THE PSI FUNCTION
Bai-Ni Guo,Feng Qi 대한수학회 2010 대한수학회보 Vol.47 No.1
In the present paper, we give two new proofs for the necessary and sufficient condition α ≤ 1 such that the function xα[ln x − ψ(x)] is completely monotonic on (0,∞).
Bai, Yujia,Huang, Wenshu,Tao, Yongxia,Feng, Zuoshan The Korean Society for Applied Biological Chemistr 2014 Applied Biological Chemistry (Appl Biol Chem) Vol.57 No.1
The precise mechanism by which asafoetida extract influenced the growth of Pleurotus ferulae mycelium was investigated using a comparative proteomic analysis approach. Two types of asafoetida extracts were added to the medium of P. ferulae, and the effects of the extract on microstructure of P. ferulae mycelium were observed. Compared to the control group, the two asafoetida extracts played a significant role in promoting the growth of P. ferulae. Two-dimensional electrophoresis and LC-MS/MS were performed to examine changes in the expression of proteins in the mycelium of P. ferulae. A total of eight differentially expressed proteins were identified, including a heat shock protein, a flavin-containing monooxygenase, and a NADPH: quinone oxidoreductase type IV, as well as hypothetical and unknown proteins. Expression change of these proteins confirmed that asafoetida extracts significantly affected P. ferulae growth, metabolism, and secondary product metabolism. These results provide new insights into biochemical mechanisms underlying the relationship between P. ferulae and asafoetida.