Experimental and numerical research on cavitating flows around axisymmetric bodies

Wei Haipeng,Fu Song,Wu Qin,Huang Biao,Wang Guoyu 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.11

We investigated the cavitating flows around different axisymmetric bodies based on experiments and numerical simulation. In the numericalsimulation, the multiphase Reynolds averaged Navier Stokes equations (RANS) were solved via the commercial computationalfluid dynamics code CFX. The modified k-w SST turbulence model was used along with the transport equation-based cavitation model. In the experiments, a high-speed video technique was used to observe the unsteady cavitating flow patterns, and the dynamic force measurementsystem was used to measure the hydrodynamics of the axisymmetric bodies under different cavitation conditions. Results areshown for the hemisphere bodies, conical bodies and blunt bodies. Reasonable agreements were obtained between the computational andexperimental results. The results show that for the hemispherical body, the cavity consists of quasi-steady transparent region and unsteadyfoggy water-vapor mixture region, which contains small-scale vortices and is dominated by bubble clusters, causing irregulardisturbances at the cavity interfaces. The curvature at the front of the conical body is larger, resulting in that the flow separates at theshoulder of the axisymmetric body. The cavity stretches downstream and reaches to a fixed cavity length and shape. For blunt bodies, theincipient cavitation number is larger than that for the hemispherical body. A large cloud cavity is formed at the shoulder of the blunt bodyin the cores of vortices in high shear separation regions and the re-entrant jet does not significantly interact with the cavity interface whenit moves upstream. As to the dynamic characteristics of unsteady cavitating flows around the axisymmetric bodies, the pulsation frequencyfor the hemispherical body is larger than that for the blunt body. For the hemispherical body, the pulsation is mainly caused bythe high-frequency, small-scale shedding at the rear end of the cavity, while for the blunt body, the main factor for the pulsation frequencyis the periodically shedding of large-scale vortex cavities.

In situ IR studies on the mechanism of methanol synthesis from CO/H2 and CO2/H2 over Cu-ZnO-Al2O3 catalyst

Wei Li,Xiaojuan Wang,Haipeng Zhang 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.4

Methanol synthesis from CO/H2 and CO2/H2 was carried out at atmospheric pressure over Cu/ZnO/Al2O3catalyst. The formation and variation of surface species were recorded by in situ FT-IR spectroscopy. The result revealed that both CO and CO2 can serve as the primary carbon source for methanol synthesis. For CO/H2 feed gas, only HCOOZn was detected; however, for CO2/H2, both HCOO-Zn and HCOO-Cu were observed, and without CH3O-Cu. HCOOZn was the key intermediate. A scheme of methanol synthesis and reverse water-gas shift (RGWS) reaction was proposed.

cDNA Cloning and Expression Analysis of a Novel Human F-Box Only Protein

Haipeng Cheng,Yushu Ma,Xiaohua Ni,Min Jiang,Lingchen Guo,Wei Jin,Weiwen Xu,Gentao Cao,Chaoneng Ji,Kang Ying,Shaohua Gu,Yuhong Ma,Yi Xie,Yumun Mao 한국분자세포생물학회 2002 Molecules and cells Vol.14 No.1

F-box proteins are an expanding family of eukaryotic proteins that are characterized by an approximately 40 amino acid motif. Some F-box proteins are critical for the controlled degradation of cellular regulatory proteins. During a large-scale sequencing analysis of a human fetal brain cDNA library, we isolated a cDNA clone that encodes a novel F-box protein. It showed a 90.0% identity with the previously isolated mouse F-box protein16 at the amino acid level. Northern blot analysis showed no detectable expression, while re-verse transcription-polymerase chain reaction analysis indicated that FBXO16 was expressed in the heart, spleen, and colon. By mapping, we localized the FBXO16 gene to the human chromosome 8p12. The FBXO16 gene consisted of 9 exons that spanned 67,816 bp of human genomic DNA.

Effect of cohesive powders on pressure fluctuation characteristics of a binary gas-solid fluidized bed

Liping Wei,Youjun Lu,Jianbo Zhu,Guodong Jiang,Jun Hu,Haipeng Teng 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.10

The effect of cohesive particles on the pressure fluctuations was experimentally investigated in a binary gassolid fluidized bed. The pressure fluctuation signals were measured by differential pressure sensors under conditions of various weight percentages of cohesive particles. The cohesive particles increased the fixed bed pressure drop per unit height and decreased the minimum fluidization velocity. The Wen & Yu equation well predicts the minimum fluidization velocity of the binary system. The addition of cohesive particles slightly decreased the bubble size in bubbling flow regime when the cohesive particles and the coarse particles mixed well, while the bubble size greatly decreased when the cohesive particles agglomerated on the bed surface. The time series of pressure fluctuations was analyzed by using the methods of time domain, frequency domain and wavelet transformation. The normalized standard deviation of pressure fluctuations decreased with increasing weight percentages of cohesive particles. A wide bandwidth frequency of 0 to 1Hz got narrower with a single peak around 0.6Hz with an increase in proportion of the cohesive particles. The meso-energy and micro-energy of pressure fluctuations were decreasing with increasing cohesive particles proportions, which indicated that adding cohesive particles could reduce the energy dissipation of bubble and particle fluctuations.

Control Algorithms of Magnetic Suspension Systems Based on the Improved Double Exponential Reaching Law of Sliding Mode Control

Jian Pan,Wei Li,Haipeng Zhang 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.6

This paper proposes an improved double power reaching law integral SMC algorithm to overcome the chattering, large overshoot, slow response. This improved algorithm has two advantages. Firstly, the designed control law can reach the approaching equilibrium point quickly when it is away from or close to the sliding surface. The chattering and response speed problems can be resolved. Secondly, the proposed algorithm has a good anti-jamming performance, and can maintain a good dynamic quality under the condition of the uncertain external disturbance. Finally, the proposed algorithm is applied to the open-loop unstable magnetic suspension system. Theoretical analysis and Matlab simulation results show that the improved algorithm has better control performances than the traditional SMC and the power reaching law integral SMC algorithm, such as less chattering, smaller overshoots, and faster response speed.

Nanocellulose: a promising nanomaterial for advanced electrochemical energy storage

Chen, Wenshuai,Yu, Haipeng,Lee, Sang-Young,Wei, Tong,Li, Jian,Fan, Zhuangjun The Royal Society of Chemistry 2018 Chemical Society reviews Vol.47 No.8

<P>Nanocellulose has emerged as a sustainable and promising nanomaterial owing to its unique structures, superb properties, and natural abundance. Here, we present a comprehensive review of the current research activities that center on the development of nanocellulose for advanced electrochemical energy storage. We begin with a brief introduction of the structural features of cellulose nanofibers within the cell walls of cellulose resources. We then focus on a variety of processes that have been explored to fabricate nanocellulose with various structures and surface chemical properties. Next, we highlight a number of energy storage systems that utilize nanocellulose-derived materials, including supercapacitors, lithium-ion batteries, lithium-sulfur batteries, and sodium-ion batteries. In this section, the main focus is on the integration of nanocellulose with other active materials, developing films/aerogel as flexible substrates, and the pyrolyzation of nanocellulose to carbon materials and their functionalization by activation, heteroatom-doping, and hybridization with other active materials. Finally, we present our perspectives on several issues that need further exploration in this active research field in the future.</P>

Grab overtaking Uber: The David versus Goliath of Ride-Hailing App in Southeast Asia

Alice Tsz Ling Tam,Alison Wai Ting Lam,Katrina Ngai Han Chiu,Leona Ying Tong Chen,Haipeng Shen,Wei Zhang Academy of Asian Business (AAB) 2018 Academy of Asian Business Review Vol.4 No.2

This case study on Grab, a locally founded ride-hailing startup in ASEAN, traces its development from its humble start to its victory of ousting Uber in 2018. This case study uncovers the elements that contributed to Grab’s success, providing inspiration on how Asian companies can possibly prevail over the more established Western counterparts despite of great adversity. The report compares the development of both Grab and Uber, followed by a discussion of turning points on how Grab played out the battle with Uber across several ASEAN countries without central jurisdiction to favor it. Factors behind the success of Grab for each turning point are closely examined. Potential difficulties faced by Grab and recommendations to solve the problems are also identified. Grab manifests the spirit of “think global and act local” to succeed in the sharing economy by putting feet on the ground and resolving real “pain points” for consumers. While there are increasing number of companies with a sharing economy business model, the conventional approach of offering a low price to customers and a high pay to employees may not guarantee success for a business anymore. This case study of Grab aims to provide insights for these enterprises to conquer the market in the competitive modern business world.