Modeling dynamic behavior of MDOF systems with multiple bilinear springs

Yali Ma,Shudong Yu,Delun Wang 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.9

A computational scheme is presented in this paper to simulate dynamical behavior of multiple degrees of freedom (MDOF) systems with multiple bilinear springs. In the proposed scheme, a bilinear spring is modeled using by two parallel springs - a primary spring and a secondary spring. The primary spring is an ordinary linear spring having identical stiffness in tension and compression, and is active for tension and compression. The secondary spring, whose stiffness characterizes the bilinearity, is active only during compression. It is employed in connection with the Newmark integration method and the linear complementarity problem (LCP) formulation to obtain time-domain responses of dynamical systems with bilinear springs due to initial disturbances and harmonic excitations. The scheme described in this paper is effective in dealing with the sudden transition from tension to compression and vice versa simultaneously for all bilinear springs. Numerical results for bilinear oscillators with finite bilinearity ratios and impact oscillators with an infinite bilinearity ratio show that the proposed bilinear spring model is accurate, generic and valid for bilinearity ratios ranging from zero to infinity. Orderly and chaotic behavior of viscously damped 3-DOF system under harmonic excitation is studied for a wide range of excitation frequencies and bilinear ratios to demonstrate the effectiveness and applicability of the proposed model for MDOF bilinear systems.

Improved Resistance Switching Characteristics of BiFeO3 Thin Film by Increasing the Annealing Temperature

Zhilei Miao,Wei Wang,Rongchun Yuan,Jun Zhu,Shudong Wu,Haitao Chen,Xianghua Zeng,Qiang Wang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.09

We have fabricated BiFeO3 thin film deposited on Pt/Ti/SiO2/Si substrates by the chemical solution deposition method. The effects of annealing temperature on the thin film structure, resistance switching (RS) properties, conduction mechanisms are investigated. It exhibits improved RS window with high ON/OFF ratio ( ~10 4) for the sample annealed at 650 ℃. XPS characterization indicates that cation ratio of Fe2+/Fe3+ is increased with increasing annealing temperature. Crystal lattice distortion generated by Fe2+ cations, along with oxygen vacancies, commonly contribute to opening the RS window and the increment of conductive filaments. The film's conduction mechanisms under different annealing temperatures are fully discussed. The RS properties of this system can be effectively improved by increasing the annealing temperature, which is crucial prerequisite for future applications of BFO-based thin film device in resistance random access memory.

Palladium supported on carbon nanofiber coated monoliths for three-phase nitrobenzene hydrogenation: Influence of reduction temperature and oxidation pre-treatment

Baolei Du,Hongjiu Su,Shudong Wang 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

Carbon nanofiber (CNF) coated monoliths with a homogeneous and consistent layer were prepared bycatalytic decomposition of ethane on Ni particles, and the CNF coated monolith supports were oxidizedusing different agents to get different oxidation degrees. The as-prepared catalysts were characterized bySEM, TG, Raman spectra, FT-IR, TPD, TPR, CO pulsar and TEM, while the behavior of Pd supported on CNFcoated monoliths were tested by liquid phase of nitrobenzene hydrogenation in a continuous flowreactor. For comparison Pd/Al2O3/cordierite was also prepared. It was found that the reductiontemperature controlled Pd dispersion, which in turn was responsible for the catalytic activity. A goodlinear relationship between nitrobenzene conversion and Pd dispersion was observed. Furthermore, Pd/CNF/cordierite showed higher nitrobenzene conversion compared with Pd/Al2O3/cordierite, indicatingCNF was a superior support. The aniline selectivity was related to the amount of surface oxygen groups(SOCs) formed during the oxidation pre-treatment. SOCs, especially carboxylic acid groups, increased asthe degree of oxidation deepened, and more amounts of SOCs on CNF surface were responsible for thelower aniline selectivity.

NOx Storage-Reduction over Pt/Mg-Al-O Catalysts with Different Mg/Al Atomic Ratios

Guangwen Chen,Hao Cheng,Shudong Wang,Diyong Wu,Yin Zhang,Henqiang Li 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.3

A series of Pt/Mg-Al-O catalysts with different Mg/Al atomic ratios were prepared. The NOx storagecapacities of these catalysts were measured by isothermal storage at 350oC. It was found that the NOx storage capacityincreased with increasing Mg/Al atomic ratios. The catalytic behaviors of Pt/Mg-Al-O and Pt/MgO were studied withstorage-reduction cycles at 400oC. Under oxidizing conditions, NOx concentration in the outlet gas gradually increasedwith time, which indicated the catalysts could store NOx effectively. After a switch from oxidizing conditions toreducing conditions, NOx desorption peak emerged immediately due to the incomplete reduction of stored NOx, whichlowered the total NOx conversion. With increasing Mg/Al atomic ratio in the catalysts, NOx conversion increases. Pt/MgO has the highest NOx conversion because of its best activity in the reduction of NOx by C3H6. It seems that withan increasing amount of MgO in the catalysts, the self-poisoning of Pt-sites by adsorbed species during the reactionof NOx with C3H6 may be inhibited effectively.

Rectifying resistance switching behaviors of SnO2 microsphere films modulated by top electrodes

Rongchun Yuan,Weiwei Xia,Mengxue Xu,Zhilei Miao,Shudong Wu,Xiuyun Zhang,Junhui He,Qiang Wang 한국물리학회 2020 Current Applied Physics Vol.20 No.3

Based on the bipolar resistive switching (RS) characteristics of SnO2 films, we have fabricated a new prototypical device with sandwiched structure of Metal/SnO2/fluorine-doped tin oxide (FTO). The SnO2 microspheres film was grown on FTO glass by template-free hydrothermal synthesis, which was evaporated with various commonly used electrodes such as aluminium (Al), silver (Ag), and gold (Au), respectively. Typical self-rectifying resistance switching behaviors were observed for the RS devices with Al and Au electrodes. However, no obvious rectifying resistance switching behavior was observed for the RS device with Ag electrode. Above results were interpreted by considering the different interface barriers between SnO2 and top metal electrodes. Our current studies pave the ways for modulating the self-rectifying resistance switching properties of resistive memory devices by choosing suitable metal electrodes.

Heat treatments of peptides from oyster (Crassostrea gigas) and the impact on their digestibility and angiotensin I converting enzyme inhibitory activity

Zixuan Guo,Fujunzhu Zhao,Hui Chen,Maolin Tu,Shuaifei Tao,Zhenyu Wang,Chao Wu,Shudong He,Ming Du 한국식품과학회 2020 Food Science and Biotechnology Vol.29 No.7

The changes of protein digestibility, the peptidesin the digestive juice and angiotensin I converting enzyme(ACE) inhibitory activity after heating of oysters wereinvestigated. The digestibility of raw oysters was 71.1%,and that of oysters heated at 100 C was 67.9%. A total of169 and 370 peptides were identified from the digestion ofraw oysters and heated oysters, respectively. According toUPLC-Q-TOF-MS spectra, the peptides with a molecularweight below 2000 Da accounted for 87.6% of the totalpeptides of raw oysters and 94% of heated oysters. Testingthe ACE inhibitory activity in vitro, the IC50 values of rawoyster and cooked oyster were 6.77 lg/mL and 3.34 lg/mL, respectively. Taken together, the results showed thatheated oysters could produce more active peptides andprovide ACE inhibitory activity.

Mesoporous silica with monodispersed pores synthesized from the controlled self-assembly of silica nanoparticles

Min Su,Hongjiu Su,Baolei Du,Xiaotong Li,Gaoyuan Ren,Shudong Wang 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.5

Silica nanoparticles with different sizes (ranging from 10 nm to 104 nm) and size distributions were synthesized by semi-batch and semi-batch/batch methods of the Stöber process. Then the amorphous silica with different surface areas (ranging from 30m2/g to 400m2/g) and pores (ranging from 3 nm to 33 nm) were obtained by various aging treatments and drying methods of the synthesized colloidal silica sol. The aging treatment resulted in the monodispersed pore distribution and decreased BET surface area of silica. The high-humidity drying method led to the mesoporous silica with uniform pores and decreased small pores. As the silica was obtained by the arrangement of silica nanoparticles, the pore diameter and pore distribution of mesoporous silica were directly related to the size and distribution of nanoparticles. Furthermore, this study offered a new thought for the synthesis of other mesoporous materials with uniform pore distributions.