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Hot Deformation Behavior and Recrystallization Mechanism in an As-Cast CoNi-Based Superalloy
Yong Guan,Yongchang Liu,Zongqing Ma,Huijun Li,Hongyao Yu 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.6
The hot deformation behavior of as-cast CoNi-based superalloy was investigated by means of hot compression tests. Thecorresponding microstructure evolution after hot deformation was examined by optical microscope, as well as the TEMtechnique. The constitutive equation and processing map as a function of deformation temperature and strain rate were developed. Results show that the efficiency peak of the processing map is 0.38 at the temperature of 1130 °C and the strain rate of0.01 s−1. The discontinuous dynamic recrystallization (DDRX) related to the strain-induced grain boundary migration (SIBM)is the dominant recrystallization mechanism during hot working. Meanwhile, the DRX also occurs by forming sub-grainsaround MC carbides and shear band. In addition, the existence of fine γ′ precipitates are found to retard the recrystallization.
Yu Guan,Tao Hu,Jiang Wu,Lili Zhao,Fengguo Tian,Wei-Guo Pan,Ping He,Xuemei Qi,Fangqin Li,Kai Xu 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.1
We used a simple method of graphene oxide (GO) preparation with different oxidation levels, and control the properties of the TiO2 nanocrystals by tuning the content and oxidation degree of GO to enhance the photocatalytic performance. During the hydrothermal reaction, reduction of GO, formation of TiO2 and chemical bonds between TiO2 and reduced graphene oxide (RGO) was achieved simultaneously. Characterization results showed that TiO2 properties such as crystalline grain and particle size could be tailored by the amount of functional groups, and that crystallinity was also controlled by GO degrees of oxidation. TiO2/RGO photocatalysts showed great efficiency of mercury oxidation, which reached 83.7% and 43.6% under UV and LED light irradiation, respectively. The effects of crystalline grain size and surface chemical properties on Hg0 removal under LED and UV light irradiation were analyzed. In addition, the properties of the photocatalysts before and after UV illumination were investigated, finding that part of Ti-OH on TiO2 surface transformed to Ti-O-Ti. In a nutshell, this work could provide a new insight into enhancing activity of photocatalysts and understanding the photocatalytic mechanism.
Yu Guan,Ya-hong Mao,Pu-xin Zhu 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.10
Poly(p-phenylene benzobisoxazole) fiber is considered as a high-performance fiber because of its high strength and excellent thermal and chemical stability. It has been used in industrial reinforcement, body armor and military camouflage. But the application of poly(p-phenylene benzobisoxazole) fiber used for protective clothing is limited because it is difficult to dye with conventional dyeing processes. In this work, a carrier dyeing method with disperse dyes was first used to dye the fiber after a pretreatment with polyphosphoric acid. The effects of the carrier structure and dyeing conditions on the color strength of dyed samples were investigated. In addition, the crystallinity and orientation degree of the poly(p-phenylene benzobisoxazole) fibers before and after pretreatment with phthalimide and benzyl benzoate were measured by X-ray diffraction and velocity-oriented test, respectively. The results suggested phthalimide and benzyl benzoate, as carrier, could effectively promote disperse dyeing of the PBO fiber pretreated with polyphosphoric acid. Meanwhile, the optimal conditions for the carrier dyeing were obtained, that is, concentration of carrier 4%, dyeing temperature 150 oC and time 120 min. By way of the carrier dyeing, the K/S value of dyed sample and the percentage of dye exhaustion were greatly improved, while the crystalline structure and orientation degree of the pretreated samples hardly changed. Furthermore, the decreases of the tensile strength and the limiting oxygen index of dyed poly(p-phenylene benzobisoxazole) sample were very little, and the color fastness was also satisfactory.
Yu-Guan Xie,Chen Xu,Hai-Bin Shi,Sheng Liu,Wei Yang,Wei Tian,Wei-Zhong Zhou 소화기인터벤션의학회 2023 International journal of gastrointestinal interven Vol.12 No.1
We here report a rare case of pyrrolidine-alkaloid-induced hepatic sinusoidal obstruction syndrome (PA-HSOS) complicated with situs inversus totalis and portal vein thrombus (PVT). The patient had abdominal distention and ascites, which were not responsive to conservative medical treatment or peritoneal drainage. Transjugular intrahepatic portosystemic shunt (TIPS) was successfully performed in the patient via the left internal jugular vein approach. After the procedure, abdominal distension and ascites gradually resolved. The TIPS procedure could be considered as a useful treatment for PA-HSOS patients with PVT.
Graph-guided joint prediction of class label and clinical scores for the Alzheimer’s disease
Yu, Guan,Liu, Yufeng,Shen, Dinggang Springer Science + Business Media 2016 BRAIN STRUCTURE AND FUNCTION Vol. No.
<P>Accurate diagnosis of Alzheimer's disease and its prodromal stage, i.e., mild cognitive impairment, is very important for early treatment. Over the last decade, various machine learning methods have been proposed to predict disease status and clinical scores from brain images. It is worth noting that many features extracted from brain images are correlated significantly. In this case, feature selection combined with the additional correlation information among features can effectively improve classification/regression performance. Typically, the correlation information among features can be modeled by the connectivity of an undirected graph, where each node represents one feature and each edge indicates that the two involved features are correlated significantly. In this paper, we propose a new graph-guided multi-task learning method incorporating this undirected graph information to predict multiple response variables (i.e., class label and clinical scores) jointly. Specifically, based on the sparse undirected feature graph, we utilize a new latent group Lasso penalty to encourage the correlated features to be selected together. Furthermore, this new penalty also encourages the intrinsic correlated tasks to share a common feature subset. To validate our method, we have performed many numerical studies using simulated datasets and the Alzheimer's Disease Neuroimaging Initiative dataset. Compared with the other methods, our proposed method has very promising performance.</P>
Fault Tolerant Strategy of Abnormal Battery Discharge
Guan Yu,Zhou Xingbo,Liu Peng,Zhao Yu 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.6
To solve the problem of abnormal battery discharge in the operation of electric vehicles, a method of fault tolerance based on data driven is proposed. First, based on the relation between transient voltage and the aging degree, battery SOC estimation model is built through LS-SVM method. Then, the fault-tolerant control scheme is put forward, which aims at abnormal discharge of power battery. When known battery exception occurs, the corresponding model control law is implemented to achieve fault tolerance control. When the unknown abnormal battery fault occurs, using dynamic data circulation way, the unknown exception model is rapidly established implementing system fault tolerant control for unknown exception. Finally, the accuracy of the method is verified by the simulation, which shows that this method is good for the fault tolerance of known and unknown faults.