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Output Feedback Adaptive Control for Stochastic Non-strict-feedback System with Dead-zone
Yumei Sun,Bingwei Mao,Hongxia Liu,Shaowei Zhou 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.10
This paper focuses on the problem of adaptive neural network (NN) control for a class of nonlinear stochastic non-strict feedback system with dead-zone input. A novel adaptive NN output feedback control approach is first proposed for stochastic non-strict feedback nonlinear systems. In order to solve the problem of dead-zone input, a linear decomposition method is proposed. On the basis of the state observer, an output feedback adaptive NN controller is designed by a backstepping approach. It is shown that the proposed controller guarantees that all the signals of the closed-loop systems are semi-globally uniformly bounded in probability. Simulation results further illustrate the effectiveness of the proposed approach.
Lignin Based Flexible Electromagnetic Shielding PU Synergized with Graphite
Jia Zhang,Yunxia Qi,Yumei Zhang,Jinchi Duan,Bairun Liu,Baijun Liu,Zhaoyan Sun,Yiquan Xu,Wei Hu,Niaona Zhang 한국섬유공학회 2021 Fibers and polymers Vol.22 No.1
In this paper, lignin (L)-based polyurethane (FeGLPU) with excellent electromagnetic shielding properties wasprepared and studied. The modified reduced iron powder was modified with KH550, and then the obtained modified reducediron powder (Fe) was mixed with lignin, polyethylene glycol 200 (PEG200), hexamethylene diisocyanate (HDI) and graphite(G) to in-situ synthesize the FeGLPU. The thermal stability, mechanical properties, electronic conductivity, and morphologyof the composite FeGLPU were characterized in detail. The electromagnetic interference shielding effectiveness (EMI SE) ofFeGLPU was tested in the frequency range of 8.2-26.5 GHz. When the content of Fe and G was fixed at 10 % and the lignincontent was 5 %, the maximum EMI SE was 21.6 dB, and the frequency width of EMI SE greater than 10 dB was 18.3 GHz. The conductivity was 4.27×10-4 S/m, and the tensile strength of Fe10G10L5PU reached 11.7 MPa. When the lignin contentincreased to be 20 %, the maximum EMI SE was 22.5 dB, and the frequency width of EMI SE greater than 10 dB was18.3 GHz. The conductivity was 1.06×10-2 S/m, and the thermal decomposition temperature T5 (5 % weight loss) reached234 °C. The obtained excellent EMI SE should be due to the synergistic effect of Fe, G and lignin. It can be observed fromthe SEM observation that the G and Fe are uniformly dispersed in PU matrix with strong interfacial interaction. It wasillustrated that the prepared FeGLPU was with efficient electromagnetic shielding properties, good mechanical properties,and high thermal stability. This lignin based electromagnetic shielding PU was proposed to have broad application prospectsdue to its low expenses and ecology friendliness.
Microstructure and Mechanical Properties of Mg–2.0Gd–1.2Y–1.0Zn–0.2Zr Alloy
Jianan Liu,Xiaoru Zhang,Wenxue Lv,Yumei Zhou,Daqing Fang,Xiangdong Ding,Jun Sun 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7
The microstructural evolution of Mg–2.0Gd–1.2Y–1.0Zn–0.2Zr (GWZK) alloy during homogenization and subsequentaging heat-treatment and the tensile properties of the peak-aged sample at various temperatures have been investigated. Thephase transformation during homogenization, static precipitation during aging, and deformation mechanisms at 250 °C aresystematically analyzed through XRD, TEM and EBSD measurements. The peak-aged GWZK alloy has good combinationof strength and ductility at elevated temperatures owing to its high thermal stability by the LPSO phases distributed alongthe grain boundaries. The change (19 MPa) in the yield strength of peak-aged samples between RT and 250 °C is mainlyrelated to easy gliding of dislocations on the non-basal planes due to the decrease in critical resolved shear stress of slip. Two strengthening models are applied to quantitatively describe the efect of {11 −2 0}훼precipitate plates on Orowanstrengthening corresponding to RT and 250 °C. Ignoring changes in solid solution strengthening and grain boundary strengthening of the peak-aged sample caused by increasing temperature, the calculated reduction value (16.5 MPa) in macroscopicyield strength from RT (based on the basal<a>slip mode) to 250 °C (based on the pyramidal<c+a>slip mode) is in goodagreement with the measured reduction value (19 MPa).
Deqing Xue,Ruihao Yuan,Dezhen Xue,Yumei Zhou,Guojun Zhang,Xiangdong Ding,Jun Sun 한국물리학회 2018 Current Applied Physics Vol.18 No.7
The damping and transformation behaviors of Ti50(Pd50−xCrx) shape memory alloys with x ranging from 4.0 to 5.0 are systematically investigated. The damping capacity (Q−1) at the martensitic transformation is found to be inversely proportional to the square root of frequency, i.e., Q−1∝ω−0.5. A relaxation peak or shoulder is observed slightly below the martensitic transformation damping peak for compositions within the compositional crossover region (4.5 ⩽x⩽ 4.8). Furthermore, the damping capacity at the martensitic transformation is smaller within the compositional crossover region (4.5 ⩽x⩽ 4.8), compared with that of compositions at both sides (x = 4.0 and x = 5.0). These observations can be ascribed to the hysteretic motion of interfaces between different phases near the compositional crossover region.
Ke Xu,Xiaosheng Yang,Dagao Sun,Xin Yang,Yumei Zhou,Wei Li,Qindan Yang,Xianjiong Yang,Rong Li,Jian Feng 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2020 NANO Vol.15 No.02
LaFeO3/NiO modified g-C3N4 nanosheets (L-N/CNS) were synthesized by a two-step method. HRTEM results showed that an intimate contact between LaFeO3, NiO and N-CNS was successfully established. Ninety percent of phenol was degraded within 120 min, and the hydrogen evolution rate of 171.2 μmol h -1 g -1 was obtained over the L-N/CNS heterojunctions under the visible-light irradiation. It was higher than that of g-C3N4 nanosheets, NiO modified g-C3N4 and LaFeO3/g-C3N4. The ·O2 - radicals acted the crucial role in the photocatalytic degradation reaction. EIS, PL and time-resolved fluorescence spectra demonstrated that L-N/CNS possessed the highest charge separation efficiency. The intimate contact between LaFeO3, NiO and g-C3N4 nanosheets promoted the separation and transfer of photo-induced electron–hole pairs and consequently prolonged the exciton lifetime, and implied more photo-induced electrons could be probably involved in the photocatalytic reactions on the surface of photocatalysts. Thus, the visible-light driven photocatalytic performances of L-N/CNS were effective. This work provided a feasible method to design and construct heterostructures for the exploitation of solar energy.
Evolution of E. coli Phytase for Increased Thermostability Guided by Rational Parameters
( Jiadi Li ),( Xinli Li ),( Yuanming Gai ),( Yumei Sun ),( Dawei Zhang ) 한국미생물생명공학회(구 한국산업미생물학회) 2019 Journal of microbiology and biotechnology Vol.29 No.3
Phytases are enzymes that can hydrolyze phytate and its salts into inositol and phosphoric acid, and have been utilized to increase the availability of nutrients in animal feed and mitigate environmental pollution. However, the enzymes’ low thermostability has limited their application during the feed palletization process. In this study, a combination of B-value calculation and protein surface engineering was applied to rationally evolve the heat stability of Escherichia coli phytase. After systematic alignment and mining for homologs of the original phytase from the histidine acid phosphatase family, the two models 1DKL and 1DKQ were chosen and used to identify the B-values and spatial distribution of key amino acid residues. Consequently, thirteen potential amino acid mutation sites were obtained and categorized into six domains to construct mutant libraries. After five rounds of iterative mutation screening, the thermophilic phytase mutant P56214 was finally yielded. Compared with the wild-type, the residual enzyme activity of the mutant increased from 20% to 75% after incubation at 90°C for 5 min. Compared with traditional methods, the rational engineering approach used in this study reduces the screening workload and provides a reference for future applications of phytases as green catalysts.