Fault-Tolerant Control of Nonlinear System

Yingwei Zhang,Shuying Wu,Yuan Wei 제어·로봇·시스템학회 2011 International Journal of Control, Automation, and Vol.9 No.6

The design strategies of fault-tolerant control system (FTCS) are developed, which are categorized into two types: redundant design and fault compensation. In the first type, a certain degree of redundancy is introduced to controller. The resulting closed-loop system is stable not only when all actuators are operational but also only when one actuator experiences fault. In the second type, the on-line fault-tolerant control (FTC) scheme is developed based on the fuzzy logic system. The closed-loop stability is established based on Lyapunov’s sense. The resulting closed-loop system is stable by using the corrective control law. Compared with the existing results, the fault is accommodated by the fault compensator. The updating control law is so derived that all the parameters of the closed-loop system are bounded. The advantage of redundant design is that it is unnecessary to know the position and magnitude of the fault and is performed without FDI, which reduce the computing time and avoid the false alarms, non-detection and delay due to FDI. The advantage of fault compensation is the dynamics caused by faults that can be accommodated online. Examples of the proposed design indicate that the approaches are effective.

PIV measurement and numerical investigation on flow characteristics of simulated fast reactor fuel subassembly

Zhang, Cheng,Ju, Haoran,Zhang, Dalin,Wu, Shuijin,Xu, Yijun,Wu, Yingwei,Qiu, Suizheng,Su, G.H. Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.5

The flow characteristics of reactor fuel assembly always intrigue the designers and the experimentalists among the myriad phenomena that occur simultaneously in a nuclear core. In this work, the visual experimental method has been developed on the basis of refraction index matching (RIM) and particle image velocimetry (PIV) techniques to investigate the detailed flow characteristics in China fast reactor fuel subassembly. A 7-rod bundle of simulated fuel subassembly was fabricated for fine examination of flow characteristics in different subchannels. The experiments were performed at condition of Re=6500 (axial bulk velocity 1.6 m/s) and the fluid medium was maintained at 30℃ and 1.0 bar during operation. As for results, axial and lateral flow features were observed. It is shown that the spiral wire has an inhibitory effect on axial flow and significant intensity of lateral flow mixing effect is induced by the wire. The root mean square (RMS) of lateral velocity fluctuation was acquired after data processing, which indicates the strong turbulence characteristics in different flow subchannels.

Semiparametric estimation methods for the accelerated failure time mixture cure model

Zhang, Jiajia,Peng, Yingwei 한국통계학회 2012 Journal of the Korean Statistical Society Vol.41 No.3

This paper provides an overview of two semiparametric estimation methods recently proposed in the literature for the accelerated failure time mixture cure model. We prove that the two estimation methods are asymptotically equivalent. A simulation is conducted to investigate the rate of convergence of the two methods. We apply these methods to fit the accelerated failure time mixture cure model to the survival times of leukemia patients receiving bone marrow transplantation.

The gradient recovery for finite volume element method on quadrilateral meshes

Yingwei Song,Tie Zhang 대한수학회 2016 대한수학회지 Vol.53 No.6

We consider the finite volume element method for elliptic problems using isoparametric bilinear elements on quadrilateral meshes. A gradient recovery method is presented by using the patch interpolation technique. Based on some superclose estimates, we prove that the recovered gradient $R(\nabla u_h)$ possesses the superconvergence: $\|\nabla u-R(\nabla u_h)\|=O(h^2)\|u\|_3$. Finally, some numerical examples are provided to illustrate our theoretical analysis.

Semiparametric estimation methods for the accelerated failure time mixture cure model

Jiajia Zhang,Yingwei Peng 한국통계학회 2012 Journal of the Korean Statistical Society Vol.41 No.3

This paper provides an overview of two semiparametric estimation methods recently proposed in the literature for the accelerated failure time mixture cure model. We prove that the two estimation methods are asymptotically equivalent. A simulation is conducted to investigate the rate of convergence of the two methods. We apply these methods to fit the accelerated failure time mixture cure model to the survival times of leukemia patients receiving bone marrow transplantation.

THE GRADIENT RECOVERY FOR FINITE VOLUME ELEMENT METHOD ON QUADRILATERAL MESHES

Song, Yingwei,Zhang, Tie Korean Mathematical Society 2016 대한수학회지 Vol.53 No.6

We consider the nite volume element method for elliptic problems using isoparametric bilinear elements on quadrilateral meshes. A gradient recovery method is presented by using the patch interpolation technique. Based on some superclose estimates, we prove that the recovered gradient $R({\nabla}u_h)$ possesses the superconvergence: ${\parallel}{\nabla}u-R({\nabla}u_h){\parallel}=O(h^2){\parallel}u{\parallel}_3$. Finally, some numerical examples are provided to illustrate our theoretical analysis.

Emerging 2D material-based nanocarrier for cancer therapy beyond graphene

Wang, Yingwei,Qiu, Meng,Won, Miae,Jung, Eugeine,Fan, Taojian,Xie, Ni,Chi, Sung-Gil,Zhang, Han,Kim, Jong Seung Elsevier 2019 Coordination Chemistry Reviews Vol.400 No.-

<P><B>Abstract</B></P> <P>2D materials (e.g., graphene, graphene analogues), with unique physical and chemical properties, shows intriguing potential for the realization of versatile biomedical applications. Tremendous attention has been attracted on 2D material based nanocarriers, which play a crucial role in therapeutic drug, gene, and biomedical agent delivery for cancer theranostics. This review provides an up-to-date review on the development of nanocarriers based on 2D materials beyond graphene, including basic and emerging synthesis methods, the catalog of 2D material-based nanocarriers, biosafety, surface functional engineering, the realization of stimuli-responsive controllable release and biomedical applications. Among the properties and performance to be summarized, there is particular focus on nanocarriers loading capability, biosafety, and therapy efficiency and so on. Finally, by addressing major issues and challenges, some prospects for future directions in this area are provided.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highlight the emerging 2D material based nanocarriers for biomedical applications. </LI> <LI> Summarized surface engineering strategy used in nanocarriers. </LI> <LI> Overview the biomedical application of 2D material nanocarriers. </LI> <LI> Give a guide to design stimuli-responsive controllable drug release strategy. </LI> <LI> Proposed insightful prospects for the future development of 2D material based nanocarriers application. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

An effective method for directly extracting lithium from a-spodumene by activated roasting and sulfuric acid leaching

Yuqing Zhang,Baozhong Ma,Yingwei Lv,Chengyan Wang,Yongqiang Chen 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.122 No.-

The global trend toward electrification has encouraged lithium’s market position to grow prominently. Spodumene is the focus of lithium extraction owing to its abundant lithium resources. In this study, anovel lithium extraction method was proposed for a-spodumene by combining activated roasting andsulfuric acid leaching. First, the thermodynamics of the roasting process demonstrated that aspodumenewas converted into b-spodumene, which reacted with CaO to produce acid-solubleLiAlSiO4 and CaSiO3 concurrently. The addition of CaO reduced the melting temperature, which promotedthe structural transformation of b-spodumene and further acid leaching. Then, the influences of variousfactors on lithium extraction were investigated by a single-factor test. A lithium leaching yield of 96.18%was obtained under optimum conditions: 20% CaO, roasting temperature of 1200 C, holding time of1.5 h, H2SO4 concentration of 120 g/L, liquid–solid ratio of 7:1 mL/g, leaching temperature of 80 Cand leaching time of 1.5 h. Finally, Li entered into leach liquor by the action of sulfuric acid, and the maincomponents of the leach residue were silicate and calcium sulfate. Compared to the conventional acidapproach, this method has a higher lithium recovery and lower energy and acid consumption (decreaseby approximately 0.42 kg/ kg).

An evaluation on in-pile behaviors of SiC_f/SiC cladding under normal and accident conditions with updated FROBA-ATF code

Chen, Ping,Qiu, Bowen,Li, Yuanming,Wu, Yingwei,Hui, Yongbo,Deng, Yangbin,Zhang, Kun Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.4

Although there are still controversial opinions and uncertainty on application of SiC_f/SiC composite cladding as next-generation cladding material for its great oxidation resistance in high temperature steam environment and other outstanding advantages, it cannot deny that SiC_f/SiC cladding is a potential accident tolerant fuel (ATF) cladding with high research priority and still in the engineering design stage for now. However, considering its disadvantages, such as low irradiated thermal conductivity, ductility that barely not exist, further evaluations of its in-pile behaviors are still necessary. Based on the self-developed code we recently updated, relevant thermohydraulic and mechanical models in FROBA-ATF were applied to simulate the cladding behaviors under normal and accident conditions in this paper. Even through steady-state performance analysis revealed that this kind of cladding material could greatly reduce the oxidation thickness, the thermal performance of UO₂-SiC was poor due to its low inpile thermal conductivity and creep rate. Besides, the risk of failure exists when reactor power decreased. With geometry optimization and dopant addition in pellets, the steady-state performance of UO₂-SiC was enhanced and the failure risk was reduced. The thermal and mechanical performance of the improved UO₂-SiC was further evaluated under Loss of coolant accident (LOCA) and Reactivity Initiated Accident (RIA) conditions. Transient results showed that the optimized ATF had better thermal performance, lower cladding hoop stress, and could provide more coping time under accident conditions.