Compressive Properties of Electron Beam Melted Ti–6Al–4V Porous Meshes with Different Struts Distributions

Zhiwei Liu,Mingjing Qi,Xiaoyu Qin,Dawei Huang,Xiaoyong Zhang,Xiaojun Yan 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.7

Structural collapse caused by uneven stress distribution is one of the main failure modes of Electron Beam Melted (EBM)Ti–6Al–4V porous meshes for medical bone implantation. In this paper, two types of porous meshes with different strutsdistributions are fabricated by EBM methods and experimentally studied through uniaxial compression tests. The first type(mesh 1) with simplified struts distribution consists of horizontal, vertical and diagonal struts, which are connected by onenode. The second type (mesh 2) has relatively complicated struts distribution with four structural nodes connected by vertical,horizontal and diagonal struts, and the inclined struts with an angle of 15° to the vertical or horizontal direction. Themechanical properties of solid Ti–6Al–4V alloy are also tested as reference for model-fitting analysis and the test resultsshow that the EBM specimen can achieve comparable tensile strength (1186.5 MPa) and elastic modulus (106.4 GPa) asthat of forging specimen. For the porous meshes, the deformation behavior of the struts along the load orientation is dominatedby buckling mechanism and the deformation behavior of the struts inclined to the load orientation is governed byboth buckling and bending mechanisms. The test results indicate that mesh 1 with relatively less inclined struts can achievebetter compressive resistance than mesh 2 when taking the factor of mesh density into consideration. Such results indicate asimple yet meaningful view that struts distributions of the porous meshes should be designed and optimized based on theirstress distribution conditions.

Toothpaste microstructure and rheological behaviors including aging and partial rejuvenation

Zhiwei Liu,Lei Liu,Huan Zhou,Jiali Wang,Linhong Deng 한국유변학회 2015 Korea-Australia rheology journal Vol.27 No.3

Toothpastes are mainly composed of a dense suspension of abrasive substances, flavors, and therapeutic ingredients in a background liquid of humectants and water, and usually exhibit complex rheological behaviors. However, the relationship between the rheology and microstructure of toothpaste remains to be studied. In this paper, three commonly used toothpastes, namely Colgate, Darlie and Yunnan Baiyao (Ynby), were qualitatively and quantitatively studied as soft glassy materials. We found that although the three toothpastes generally behaved in similar fashion in terms of rheology, each particular one was distinct from others in terms of the quantitative magnitude of the rheologcial properties including thixotropy, creep and relaxation, yield stress, and power-law dependence of modulus on frequency. In addition, the history-dependent effects were interpreted in terms of aging and rejuvenation phenomena, analogous to those existing in glassy systems, and Ynby seemed to result in greater extent of aging and rejuvenation as compared to the other two. All these differences in toothpaste rheology may well be attributed to the different microscopic network microstructures as observed in this study. Therefore, this study provides first evidence of microstructurebased rheological behaviors of toothpaste, which may be useful for optimizing its composition, manufacturing processing as well as end-user applications

兩漢王朝政治中的孔廟祀與孔子崇拜

( Liu Zhiwei ) 성균관대학교 유교문화연구소 2005 儒敎文化硏究(中文版) Vol.5 No.-

There are a lot of academic studies on the influence of Confucius and Confucianism on the politics of the feudal dynasty. However, there seems to be insufficient attention to the complex and interdependent relationship between Wang Tong represented by the feudal autocratic emperor and Jiao Tong represented by Confucianism. According to Confucianism, the ideal state of Wang Tong and Jiao Tong is to achieve a high degree of unity in the sense of orthodoxy. The reality of feudal dynasty politics is that it often conflicts with Confucianism’s pursuit, which makes Wang Tong superior to Confucianism, despising, suppressing, and persecuting Confucianism. On the other hand, Confucian ideal person firmly believes that Confucianism as the highest pursuit goal, consciously assumes the responsibility of checking and balancing. Therefore, it is necessary to accurately grasp the essential relationship between the feudal princely rule and the religious rule, to avoid the superficiality, generality, vagueness, and one-sidedness. With this as a guide, this article tries to discuss the complex similarities and differences between the feudal politics and the religious ancestors embodied in the Confucian temple services and worships in the Han Dynasty.

Constrained State Estimation via Projection based Optimized Parameters UKF

Yuanyuan Liu,Jingbiao Liu,Zhiwei He 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.11

The unscented Kalman filter (UKF) has become a popular method for nonlinear state estimation during the last decade. However, the conventional UKF may not be suitable for real-world applications with state constrains that stem from physical definitions, physical laws or model restrictions. A UKF based method with optimized parameters was proposed in this paper to handle state constraints via the projection of sigma points. In the proposed method, the generated sigma points that violate the state constraints were projected onto the constraint boundary first. The three free parameters of the UKF, i.e., α ,β ,κ , were then optimized using a Gaussian process optimization (GPO) method. Simulations indicate that the proposed optimized UKF algorithm with the projection of sigma points can handle constrained state estimation problem effectively and efficiently.

State of Charge Estimation for Li-Ion Batteries Based on an Unscented H-Infi nity Filter

Yuanyuan Liu,Tiantian Cai,Jingbiao Liu,Mingyu Gao,Zhiwei He 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.6

The state of charge (SOC) of lithium-ion batteries refl ects their remaining capacity. Accurate estimation of SOC helps battery safety and is benefi cial to the effi cient management of batteries. The charging and discharging processes of lithium-Ion batteries are very complicated, and it is diffi cult to obtain accurate SOC estimation results. Therefore, it is important to study improved algorithms for SOC estimation for this nonlinear non-Gaussian battery system. In this paper, we propose an unscented H-infi nity fi lter (UHF) based SOC estimation method, which combines the advantages of both the unscented Kalman fi lter (UKF) and the H-infi nity fi lter (HF). The UKF propagates the sigma points through the nonlinear system and does not need the fi rst-order linear approximation of the system equation, while the HF can suppress the non-Gaussian noise in the system to the greatest extent. The proposed UHF based SOC estimation algorithm is verifi ed and evaluated in the battery management system, and further optimized in practical problems. Experimental results show that the proposed UHF based algorithm can perform accurate SOC estimation for lithium-ion batteries, and is superior to the UKF based SOC estimation.

Modeling Method for Predicting the Shelf Life of Spare Parts under Automatic Modeling Process

Zhiwei Li,Qi Gao,Xinliang Jiang,Shenyang Liu,Tielu Gao 보안공학연구지원센터 2015 International Journal of u- and e- Service, Scienc Vol.8 No.9

A modeling method which can predict the shelf life of various types of spare parts in a relatively short time is put forward in this article. At present, it is difficult to solve the problem of mass modeling because the shelf life prediction models for different kinds of spare parts are of great diversification. In this paper, the best fitting nonlinear variables are selected by Gram-Schmidt regression method, and the detailed steps of automatic modeling process are given, which have advantages of strong robustness and are easy in programming. Especially, it can eliminate the influence of multicollinearity among alternative models effectively. By using natural rubber heating elongation data, an example is taken to demonstrate the process of automatic modeling. The nonlinear regression models selected by automatic modeling process are consistent in Dakin equation, and the predict values of natural rubber shelf life are included in the storage period given by manufacturing plant.

Joint Deployment and Trajectory Optimization in UAV-Assisted Vehicular Edge Computing Networks

Zhiwei Wu,Zilin Yang,Chao Yang,Jixu Lin,Yi Liu,Xin Chen 한국통신학회 2022 Journal of communications and networks Vol.24 No.1

As the general mobile edge computing (MEC)scheme cannot adequately handle the emergency communicationrequirements in vehicular networks, unmanned aerial vehicle(UAV)-assisted vehicular edge computing networks (VECNs) areenvisioned as the reliable and cost-efficient paradigm for themobility and flexibility of UAVs. UAVs can perform as thetemporary base stations to provide edge services for road vehicleswith heavy traffic. However, it takes a long time and huge energyconsumption for the UAV to fly from the stay charging stationto the mission areas disorderly. In this paper, we design a predispatchUAV-assisted VECNs system to cope with the demandof vehicles in multiple traffic jams. We propose an optimalUAV flight trajectory algorithm based on the traffic situationawareness. The cloud computing center (CCC) server predictsthe real-time traffic conditions, and assigns UAVs to differentmission areas periodically. Then, a flight trajectory optimizationproblem is formulated to minimize the cost of UAVs, while boththe UAV flying and turning energy costs are mainly considered. Inaddition, we propose a deep reinforcement learning(DRL)-basedenergy efficiency autonomous deployment strategy, to obtain theoptimal hovering position of UAV at each assigned mission area. Simulation results demonstrate that our proposed method canobtain an optimal flight path and deployment of UAV with lowerenergy consumption.

Stability and non-stationary vibration analysis of beams subjected to periodic axial forces using discrete singular convolution

Zhiwei Song,Wei Li,Guirong Liu 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.44 No.4

Dynamic instability of beams subjected to periodic axial forces is studied using the discrete singular convolution (DSC) method with the regularized Shannon’s delta kernel. The principal regions of dynamic instability under different boundary conditions are examined in detail, and the non-stationary vibrations near the stability-instability critical regions have been investigated. It is found that the results obtained by using the DSC method are consistent with the analytical solutions, which shows that the DSC algorithm is suitable for the problems considered in this study. It was found that there is a narrow region of beat vibration existed in the vicinity of one side (θ/Ω > 1) of the boundaries of the instable region for each condition.

Multi-objective optimum design of fast tool servo based on improved differential evolution algorithm

Zhiwei Zhu,Xiaoqin Zhou,Qiang Liu,Shaoxin Zhao 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.12

The flexure-based mechanism is a promising realization of fast tool servo (FTS), and the optimum determination of flexure hinge parameters is one of the most important elements in the FTS design. This paper presents a multi-objective optimization approach to optimizing the dimension and position parameters of the flexure-based mechanism, which is based on the improved differential evolution algorithm embedding chaos and nonlinear simulated anneal algorithm. The results of optimum design show that the proposed algorithm has excellent performance and a well-balanced compromise is made between two conflicting objectives, the stroke and natural frequency of the FTS mechanism. The validation tests based on finite element analysis (FEA) show good agreement with the results obtained by using the proposed theoretical algorithm of this paper. Finally, a series of experimental tests are conducted to validate the design process and assess the performance of the FTS mechanism. The designed FTS reaches up to a stroke of 10.25 μm with at least 2 kHz bandwidth. Both of the FEA and experimental results demonstrate that the parameters of the flexure-based mechanism determined by the proposed approaches can achieve the specified performance and the proposed approach is suitable for the optimum design of FTS mechanism and of excellent performances.

DESIGN AND BRAKING STABILITY ANALYSIS OF A NOVEL INTERNAL PUMP-HYDRAULIC RETARDER AXLE FOR HEAVY ARTICULATED VEHICLE

Zhiwei Gao,Desheng Li,Zongqiang Liu,Lezhi Ye 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.5

The retarder is widely used to ensure braking safety in heavy vehicles due to its noncontact braking characteristics. Currently, retarders are generally mounted on tractors, but semi-trailers have greater inertia and are prone to accidents. Therefore, the semi-trailer’s brakes have to work frequently to maintain stability during downhill braking, which causes the brakes to generate high temperatures or even failure. Based on the above problems, a novel internal pump-hydraulic retarder axle (IP-HRA) is proposed, which integrates the pump and hydraulic retarder (HR) into the support axle. The prototype of the IP-HRA was made and a bench test was conducted. In the experiment, the single-side braking power of the IP-HRA reaches 300 kW and its torque can be controlled by adjusting the outlet pressure. A co-simulation model of articulated vehicles is established to predict the braking state by computer solutions. Based on the experimental data, the methods of IP-HRA braking semi-trailer and traditional HR braking tractor are compared. The results of co-simulation show that the IP-HRA is more conducive to the braking stability of the articulated vehicle than the traditional HR when only retarder is used. Finally, the braking time and braking deceleration of IP-HRA are verified by road experiments.