Shell-wise Ferrimagnetic Properties of Free Iron Icosahedral Clusters from Ab initio Calculations

Zhida Cheng,Tao Ling,Jing Zhu 한국자기학회 2008 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

Characteristic of SiC Slurry in Ultra Precision Lapping of Sapphire Substrates

Tao Yin,ZhiDa Wang,Toshiro Doi,Syuhei Kurokawa,Zhe Tan,XiaoKang Ding,Huan Lin 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.6

A method is proposed in this paper to prepare a SiC slurry with SiC particles selected by an ultrasonic-assisted elutriation method to reduce substrate surface damage caused by abrasive particles during lapping. Sapphire substrate lapping experiments were carried out using the prepared SiC slurry, and the lapping performance of the slurry was analyzed. The experimental results show that the SiC particle size is a factor that directly affects the material removal rate and surface roughness Ra, of sapphire substrates. When a SiC slurry with a particle size of 630 nm was used, the material removal rate was 508 nm/h, and the surface roughness Ra was 1.9 nm; increasing the slurry concentration and the platen rotating speed can improve the material removal rate. In addition, the agglomeration of SiC particles in the slurry depends on the pH of the slurry. Efficient precision lapping of sapphire substrates can be achieved by selecting appropriately sized SiC particles and by adjusting the slurry pH to control the agglomeration and dispersion of SiC particlesto further reduce the scratches on the substrate surface during the lapping process.

Aerodynamic characteristics investigation of Megane multi-box bridge deck by CFD-LES simulations and experimental tests

Elena Dragomirescu,Zhida Wang,Michael S. Hoftyzer 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.22 No.2

Long-span suspension bridges have evolved through the years and with them, the bridge girder decks improved as well, changing their shapes from standard box-deck girders to twin box and multi-box decks sections. The aerodynamic characteristics of the new generation of twin and multiple-decks are investigated nowadays, to provide the best design wind speeds and the optimum dimensions such bridges could achieve. The multi-box Megane bridge deck is one of the new generation bridge decks, consisting of two side decks for traffic lanes and two middle decks for railways, linked between them with connecting beams. Three-dimensional CFD simulations were performed by employing the Large Eddy Simulation (LES) algorithm with a standard Smagorinsky subgrid-scale model, for Re = 9.3 x 107 and angles of attack a = -4, -2, 0, 2 and 4. Also, a wind tunnel experiment was performed for a scaled model, 1:80 of the Megane bridge deck section, for Re = 5.1 x 105 and the aerodynamic static coefficients were found to be in good agreement with the results obtained from the CFD-LES model. However the aerodynamic coefficients determined individually, from the CFD-LES model, for each of the traffic and railway decks of the Megane bridge, varied significantly, especially for the downstream traffic deck. Also the pressure distribution and the effect of the spacing between the connecting beams, on the wind speed profiles showed a slight increase in turbulence above the downstream traffic and railway decks.

Aerodynamic characteristics investigation of Megane multi-box bridge deck by CFD-LES simulations and experimental tests

Dragomirescu, Elena,Wang, Zhida,Hoftyzer, Michael S. Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.22 No.2

Long-span suspension bridges have evolved through the years and with them, the bridge girder decks improved as well, changing their shapes from standard box-deck girders to twin box and multi-box decks sections. The aerodynamic characteristics of the new generation of twin and multiple-decks are investigated nowadays, to provide the best design wind speeds and the optimum dimensions such bridges could achieve. The multi-box Megane bridge deck is one of the new generation bridge decks, consisting of two side decks for traffic lanes and two middle decks for railways, linked between them with connecting beams. Three-dimensional CFD simulations were performed by employing the Large Eddy Simulation (LES) algorithm with a standard Smagorinsky subgrid-scale model, for $Re=9.3{\times}10^7$ and angles of attack ${\alpha}=-4^{\circ}$, $-2^{\circ}$, $0^{\circ}$, $2^{\circ}$ and $4^{\circ}$. Also, a wind tunnel experiment was performed for a scaled model, 1:80 of the Megane bridge deck section, for $Re=5.1{\times}10^5$ and the aerodynamic static coefficients were found to be in good agreement with the results obtained from the CFD-LES model. However the aerodynamic coefficients determined individually, from the CFD-LES model, for each of the traffic and railway decks of the Megane bridge, varied significantly, especially for the downstream traffic deck. Also the pressure distribution and the effect of the spacing between the connecting beams, on the wind speed profiles showed a slight increase in turbulence above the downstream traffic and railway decks.

Online Integrated Development Environment for MapReduce Programming

Zhiqiang Ma,Shuangtao Yang,Zhida Shi,Rui Yan 보안공학연구지원센터 2016 International Journal of u- and e- Service, Scienc Vol.9 No.6

Though MapReduce programming model simplifies the development of parallel program, ordinary users have difficulties in setting up the development environment for MapReduce. The online integrated development environment for MapReduce programming can solve this problem, thus users need not build the environment themselves, only need to focus on the logical design of the parallel program. During the software construction, the problem of independent space setting and naming conflict of the file in the multi-user environment, and the problem of online compiling, execution and instant feedback message to client are solved. The software has been deployed and tested in Hadoop cluster, and can meet users’ basic requirements for the development of MapReduce.

Characteristics analysis of rotor-rolling bearing coupled system with fit looseness fault and its verification

Wang Haifei,Guan Xiaoying,Chen Guo,Gong Junjie,Yu Liang,Yuan Shijie,Zhu Zhida 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1

Outer ring of bearing fit looseness fault is a common fault. Scratch often appears in the inner surface of pedestal. The fit looseness fault mechanism is not clear. For rotor-rolling bearing system with fit looseness fault between rotor-bearing outer ring and pedestal, a rotor coupling dynamic model that the interaction of bearing outer ring and pedestal are considered. This model is different from the universal rubbing model, where the directions of relative motion between rotor and stator are not considered. Numerical integration method is used to obtain the response of the system where the rotor is established by FEM and the bearing outer ring and pedestal are established by lumped mass model. Firstly, modal test results and simulation results were used to verify the correctness of this model. Secondly, the role of tightening torque between bearing outer ring and pedestal is considered, and the response characteristics of bearing and rotor are analyzed when fit looseness fault is considered. Finally, comparing the simulation results with test results, the waveform and spectrum are similar, which verifies the correctness of the fit looseness model. The fit looseness fault characteristics are that the acceleration after noise reduction shows periodic impact, up and down asymmetry, multiple frequencies appear. A method by increasing tightening torque is put forward to control the vibration caused by fit looseness fault.

An Investigation into the Characteristics of a Novel Rotatable Pantograph Catenary System for High-Speed Trains

Xiao Song,Luo Yuanpei,Wu Jingchi,Zhang Can,Rao Yang,Wu Guangning,Deng Zhida,Sykulski Jan K. 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.3

High speed trains receive traction electrical energy from a high-voltage catenary via a pantograph catenary system (PCS). As the velocity of trains increases, the traditional PCSs face signifi cant challenges, such as strong aero resistance under highspeed conditions, severe electrochemical corrosion caused by poor contact between the pantograph strip and the catenary, harmful wear both on the pantograph strip and the contact wire produced by high-speed sliding friction between them, etc. The eff ectiveness and reliability of the PCS has a direct impact on the performance and safety of the HTS power supply. In order to alleviate some of these bottleneck eff ects related to the operation of the currently used PCSs, especially under high-speed conditions, this paper proposes a novel confi guration where rotatable pantograph rollers replace the currently used pantograph strips. As the sliding friction is now replaced by rotating friction, this has numerous benefi ts, such as less friction heat, better heat dispersion and improved catenary-tracking performance. Moreover, should the whole system be modularized, it could adapt to diff erent levels of traction power through adjusting the number of rollers.

In vitro Antioxidant Activities of Proanthocyanidins Extracted from the Lotus Seedpod and Ameliorative Effects on Learning and Memory Impairment in Scopolamine-induced Amnesia Mice

Juan Xiao,Shuyi Li,Yong Sui,Xiaopeng Li,Qian Wu,Ruifen Zhang,Mingwei Zhang,Bijun Xie,Zhida Sun 한국식품과학회 2015 Food Science and Biotechnology Vol.24 No.4

The antioxidant activity of proanthocyanidins extracted from the lotus seedpods (LSPC) in vitro and ameliorative effects on memory impairment induced using scopolamine in mice were studied. 2,2-diphenyl-1- picrylhydrazyl (DPPH) radical scavenging ability, oxygen radical absorbance capacity, and cellular antioxidant activity assays revealed a potent LSPC antioxidant activity. Y-maze and step-down avoidance testing showed that LSPC administration at 30, 60, and 90 mg/kg ameliorated memory impairment. LSPC improved glutathione peroxidase and superoxide dismutase activities, inhibited activities of monoamine oxidase-B, total nitric oxide synthase, neuronal nitric oxide synthase, and acetylcholinesterase, and had no influence on inducible nitric oxide synthase and nitric oxide levels in the brain. LSPC ameliorated scopolamineinduced memory impairment based on improvement of the antioxidant system and cholinergic activity, which may be associated with potent antioxidant ability.

Active control of amplitude and phase of high-power RF systems in EAST ICRF heating experiments

Zhu Guanghui,Liu Lunan,Mao Yuzhou,Zhang Xinjun,Guo Yaoyao,Ai Lin,Jiang Runhao,Qin Chengming,Zhang Wei,Yang Hua,Yuan Shuai,Wang Lei,Ju Songqing,Wang Yongsheng,Sun Xuan,Yang Zhida,Wang Jinxin,Cheng Yan 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.2

The EAST ICRF system operating space has been extended in power and phase control with a low-level RF system for the new double-strap antenna. Then the multi-step power and periodic phase scanning experiment were conducted in L-mode plasma, respectively. In the power scanning experiment, the stored energy, radiation power, plasma impedance and the antenna's temperature all have positive responses during the short ramp-ups of PL;ICRF. The core ion temperature increased from 1 keV to 1.5 keV and the core heating area expanded from jZj 5 cmto jZj 10 cm during the injection of ICRF waves. In the phasing scanning experiment, in addition to the same conclusions as the previous relatively phasing scanning experiment, the superposition effect of the fluctuation of stored energy, radiation power and neutron yield caused by phasing change with dual antenna, resulting in the amplitude and phase shift, was also observed. The active control of RF output facilitates the precise control of plasma profiles and greatly benefits future experimental exploration.