Biodegradable Magnesium Alloy Stents as a Treatment for Vein Graft Restenosis

Yugang Li,Lei Wang,Shanshan Chen,Dan Yu,Weifeng Sun,Shijie Xin 연세대학교의과대학 2019 Yonsei medical journal Vol.60 No.5

Purpose: To explore the effects of biodegradable magnesium alloy stents (BMAS) on remodeling of vein graft (VG) anastomoticrestenosis. Materials and Methods: To establish a VG restenosis model, seventy two New Zealand rabbits were randomly divided into threegroups according to whether a stent was implanted in the graft vein or not. BMASs and 316L stainless steel stents were implantedin BMAS and 316L groups, respectively, while no stent was implanted in the no-treatment control group (NC group). Loss of lumendiameter in the graft vein was measured in all three groups. Upon harvesting VG segments to evaluate intimal proliferationand re-endothelization, the degradation and biological safety of the stents were observed to explore the effects of BMAS on VGremodeling. Results: Model establishment and stent implantation were successful. The BMAS reduced lumen loss, compared with the controlgroup (0.05±0.34 mm vs. 0.90±0.39 mm, p=0.001), in the early stage. The neointimal area was smaller in the BMAS group than the316L group after 4 months (4.96±0.66 mm2 vs. 6.80±0.69 mm2, p=0.017). Re-endothelialization in the BMAS group was better thanthat in the 316L group (p=0.001). Within 4 months, the BMAS had degraded, and the magnesium was converted to phosphorusand calcium. The support force of the BMAS began to reduce at 2–3 months after implantation, without significant toxic effects. Conclusion: BMAS promotes positive remodeling of VG anastomosis and has advantages over the conventional 316L stents in thetreatment of venous diseases.

Dynamic Modeling and Adaptive Neural-Fuzzy Control for Nonholonomic Mobile Manipulators Moving on a Slope

Yugang Liu,Yangmin Li 대한전기학회 2006 International Journal of Control, Automation, and Vol.4 No.2

This paper addresses dynamic modeling and task-space trajectory following issues for nonholonornic mobile manipulators moving on a slope. An integrated dynamic modeling method is proposed considering nonholonomic constraints and interactive motions. An adaptive neural-fuzzy controller is presented for end-effector trajectory following, which does not rely on precise apriori knowledge of dynamic parameters and can suppress bounded external disturbances. Effectiveness of the proposed algorithm is verified through simulations.

AQUEOUS SYNTHESIS OF HIGH QUANTUM YIELD AND MONODISPERSED THIOL-CAPPED CdxZn1-xTe QUANTUM DOTS BASED ON ELECTROCHEMICAL METHOD

JUNWEI LI,YANG JIANG,YUGANG ZHANG,DI WU,ANQI LUO,ZHONGPING ZHANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2012 NANO Vol.7 No.2

A facile green approach has been developed to control the growth regime in the aqueous synthesis of CdxZn1-xTe semiconductor quantum dots (QDs) based on the electrochemistry method. The Low growth temperature and slow injection of Te precursor are used to prolong the diffusion controlled stage and thus suppress Ostwald ripening during the nanocrystal growth. The experimental results showed that a low concentration of Te precursor will definitely influence the growth procedure. The UV–visible absorption spectra, as well as transmission electron microscopy (TEM) shows the QDs a good monodispersity at any interval of the reaction procedure. The high-resolution transmission electron microscopy (HRTEM) images and powder X-ray diffraction (XRD) pattern suggested that the as-prepared QDs have high crystallinity and cubic structure. The size and composition-dependent fluorescent emission wavelength of the resultant CdxZn1-xTe alloyed QDs can be tuned from 460 to 610 nm, and their photoluminescent quantum yield can reach up to 70%. Especially in the wavelength range of 510–578 nm, the overall PL QYs of the as-prepared CdxZn1-xTe QDs were above 50%. The current work suggests that electrochemical method is an attractive approach to the synthesis of high-quality II-VI ternary alloyed semiconductor QDs at large-scale with a prominent cost advantage.

Prediction Model of Net Cutting Specific Energy Based on Energy Flow in Milling

Chunxiao Li,Guoyong Zhao,Yugang Zhao,Shuang Xu,Zhifu Zheng 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.5

Net cutting specific energy ( NCSE ) reflects the actual cutting energy efficiency. Establishing a NCSE prediction model is helpful to analyze the energy consumption characteristics of machine tools. As so far, few studies have focused on the NCSE prediction in the way of energy flow. Therefore, based on the flow direction of cutting energy, a mathematical model for predicting NCSE is proposed in this paper. During milling, the energy used for cutting can be divided into forming surface energy, material removing energy and additional load energy. Thus, the NCSE model is decomposed into three sub-models. Firstly, in the cutting process of AISI 304 stainless steel, the phase transition of austenite to martensite on the machined surface is induced by parts of cutting energy, and then work hardening occur. Furthermore, the forming surface specific energy prediction model is established based on surface hardness. Secondly, the models of material removing energy and additional load energy are developed respectively with the material removal rate and spindle speed. The above sub-models are integrated into the NCSE prediction model with the determination coefficient R 2 of 0.982, and average prediction accuracy of 96.77%. Finally, the influence of input variables on NCSE and the energy consumption proportion are revealed. Among them, the forming surface specific energy, material removing specific energy and additional load specific energy account for 8.26%, 32.63% and 59.11% on NCSE respectively. The proposed model can not only predict the overall cutting energy consumption, but also predict the energy consumption of each sub-model. The research provides a new idea for analyzing cutting energy characteristics and improving processing theory.

Comparion of Seismic Response of Single-layer Reticulated Dome under Unform and Incoherence Three-directional Excitations

Feng Fan,Yugang Li,Xudong Zhi,Lu Li 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.4

Seismic ground motions at structural supports are spatially varying and incoherent. The spatial incoherency effects shouldbe considered for structures with large span and multiple supports. Two single-layer reticulated domes of 120m span, with andwithout substructures under incoherent multiple supports and uniform excitations were modeled and analysed in this study. Time-history responses of structures are obtained and compared for simulated ground motion records. For the simulation, useof existing phase difference spectrum models and coherence models were considered, and three-directional excitations (twohorizontal directions and vertical direction) are considered. The analysis results show that the spatial coherency effect caninfluence the seismic responses of reticulated domes. The results also indicate that the seismic spatial coherency of all threedirections can be important, especially for structures without flexible substructures.

Observer-Based H∞ Control for Networked Systems with Consecutive Packet Delays and Losses

Fuwen Yang,Yugang Niu,Wu Wang,Yongmin Li 제어·로봇·시스템학회 2010 International Journal of Control, Automation, and Vol.8 No.4

This paper considers the control problem for networked control systems (NCSs) with unreliable data communication. The unreliable data communication simultaneously exists in both control channel (from controller to actuator) and measurement channel (from sensor to controller) and may cause consecutive packet delays and losses. A new model is established based on all possible consecutive packet delays and losses. The observer-based controller is designed to exponentially stabilize the networked system in the sense of mean square, and also achieve the prescribed H∞ disturbance attenuation level. An iterative algorithm is developed to compute the optimal H∞ disturbance attenuation and the controller parameters by solving the semi-definite programming problem via interior-point approach. An illustrative example is provided to show the applicability of the proposed method.