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Chengyuan Cheng,Weiyong Ying,Haitao Zhang,Dingye Fang 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.7
The reaction kinetics of the dimethyl ether synthesis from hydrogen-rich synthesis gas over bi-functional catalyst was investigated using an isothermal integral reactor at 220-260 oC temperature, 3-7MPa pressure, and 1,000-2,500 mL/g·h space velocity. The H_2/CO ratio of the synthetic gas was chosen between 3 : 1 and 6 : 1. The bi-functional catalyst was prepared by physically mixing commercial CuO/ZnO/Al_2O_3 and γ-alumina, which act as methanol synthesis catalyst and dehydration catalyst, respectively. The three reactions, including methanol synthesis from CO and CO_2as well as methanol dehydration, were chosen as independent reactions. The Langmuir-Hinshelwood kinetic models for dimethyl ether synthesis were adopted. Kinetics parameters were obtained using the Levenberg-Marquardt mathematical method. The model was reliable according to statistical and residual error analyses. The effects of different process conditions on the reactor performance were also investigated.
A multi-user selective undo/redo approach for collaborative CAD systems
Cheng, Yuan,He, Fazhi,Xu, Bin,Han, Soonhung,Cai, Xiantao,Chen, Yilin Society for Computational Design and Engineering 2014 Journal of computational design and engineering Vol.1 No.2
The engineering design process is a creative process, and the designers must repeatedly apply Undo/Redo operations to modify CAD models to explore new solutions. Undo/Redo has become one of most important functions in interactive graphics and CAD systems. Undo/Redo in a collaborative CAD system is also very helpful for collaborative awareness among a group of cooperative designers to eliminate misunderstanding and to recover from design error. However, Undo/Redo in a collaborative CAD system is much more complicated. This is because a single erroneous operation is propagated to other remote sites, and operations are interleaved at different sites. This paper presents a multi-user selective Undo/Redo approach in full distributed collaborative CAD systems. We use site ID and State Vectors to locate the Undo/Redo target at each site. By analyzing the composition of the complex CAD model, a tree-like structure called Feature Combination Hierarchy is presented to describe the decomposition of a CAD model. Based on this structure, the dependency relationship among features is clarified. B-Rep re-evaluation is simplified with the assistance of the Feature Combination Hierarchy. It can be proven that the proposed Undo/Redo approach satisfies the intention preservation and consistency maintenance correctness criteria for collaborative systems.
Field Weakening Control of a PM Electric Variable Transmission for HEV
Cheng, Yuan,Bouscayrol, Alain,Trigui, Rochdi,Espanet, Christophe,Cui, Shumei The Korean Institute of Electrical Engineers 2013 Journal of Electrical Engineering & Technology Vol.8 No.5
This paper presents the control of a Permanent Magnet Electric Variable Transmission (PM-EVT) for Hybrid Electric Vehicles (HEVs). Consisting of two electric machines, the EVT realizes the power split function in an electromagnetic way rather than in a mechanical way. A specific PM-EVT has been designed for Toyota Prius II. The control scheme of the entire vehicle is deduced using the Energetic Macroscopic Representation methodology. The energy management strategy yields local control references. A specific attention is paid for the field weakening for wide speed range. Simulation results are provided to illustrate the EVT modeling and control.
A double integral characterization of a Bergman type space and its M\"obius invariant subspace
Cheng Yuan,Hong-Gang Zeng 대한수학회 2019 대한수학회보 Vol.56 No.6
This paper shows that if $1<p<\infty$, $\alpha\ge-n-2$, $\alpha>-1-\frac{p}{2} $ and $f$ is holomorphic on the unit ball $\bbn$, then $$\ibn |Rf(z)|^p(1-|z|^2)^{p+\alpha} \rd v_\alpha(z)<\infty$$ if and only if $$\ibn\ibn\frac{|f(z)-f(w)|^p}{|1-\langle z,w\rangle|^{n+1+s+t-\alpha}} (1-|w|^2)^s(1-|z|^2)^t \rd v(z)\rd v(w)<\infty,$$ where $s,t>-1$ with $\min(s,t)>\alpha $.