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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.
Guan, Xiang-Yu,Leem, Jung Woo,Lee, Soo Hyun,Jang, Ho-Jin,Kim, Jeong-Ho,Hann, Swook,Yu, Jae Su Optical Society of America 2015 Applied Optics Vol.54 No.5
<P>We fabricated amorphous silicon (a-Si)-based distributed Bragg reflectors (DBRs) consisting of alternating dense/porous films (i.e., pair) for a center wavelength (λ(c)) of 0.96 μm by oblique angle deposition (OAD) technique using an electron-beam evaporation system. The dense (high refractive index, i.e., high-n) and porous (low-n) a-Si films were deposited at two incident vapor flux angles of 0 and 80 in the OAD, respectively. Their optical reflectance characteristics were investigated in the wavelength range of 0.6-1.5 μm, including theoretical comparison using a rigorous coupled-wave analysis method. Above three pairs, the reflectivity (R) of a-Si DBRs was almost saturated at wavelengths around 0.96 μm, exhibiting R values of >97%. For the a-Si DBR with only three pairs, a broad normalized stop bandwidth (δλ/λ(c)) of 22.5% was obtained at wavelengths of 0.87-1.085??μm, keeping high R values of >95%. To simply demonstrate the feasibility of device applications, the a-Si DBR with three pairs was coated as a high-reflection layer at the rear facet of GaAs/InGaAs quantum-well laser diodes (LDs) operating at λ=0.96??μm. For the LDs coated with three-pair a-Si DBR, external differential quantum efficiency (η(d)) was nearly doubled compared to the uncoated LDs, indicating the η(d) value of 50.6% (i.e., η(d)25.5% for the uncoated LDs).</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.
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>
Compounds from a jellyfish-derived fungus Aspergillus fumigates
Guan-yu Tao,Juan Liu,정지형,Wei Guo,Xiao-qiong Wen,Yonghong Liu 한국생약학회 2016 Natural Product Sciences Vol.22 No.2
Six compounds were isolated from the secondary metabolites of the jellyfish-derived fungus Aspergillus fumigates, whose structures were identified by chemical methods and spectroscopic analysis as pseurotin F1 (1), azaspirofurans B (2), (22E, 24R)-24-methyl-5a-cholesta-7,22-diene-3b,5,6b-triol (3), 5a,8a-epidioxyergosta-6,22-dien-3b-o1 (4), cyclo-(L-Pro-L-Tyr) (5), fumitremorgin C (6). The compounds 1 - 5 were isolated from the fungus Aspergillus fumigates for the first time. The isolated compounds (1 - 6) were evaluated for antibiotic activity and cytotoxicity against six bacterial strains and ten human tumor cell lines, respectively.
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.
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.