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Search Results: 1 - 10 of 3787 matches for " Yanpeng Qu "
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Numerical Investigation on the Features of Gasoline Mixture Flow Field with Rotary Jet Mixing
Numerical Investigation on the Features of Gasoline Mixture Flow Field with Rotary Jet Mixing

Songying Chen,Longhao Xiang,Yanpeng Qu
- , 2018, DOI: 10.15918/j.jbit1004-0579.17097
Abstract: Employing the standard k-ε turbulent model and slipping grid technique, distributions of velocity and dynamic pressure and mixing time was numerically investigated to research the gasoline flow features and mixing efficiency in a gasoline mixture tank with a rotary jet mixing (RJM) system installed at the bottom center. The simulation results showed that the RJM system can achieve fully circular stir without blind corner, reaching high mixing efficiency in the mixing process of gasoline from different refining line. The mixing density difference met the mixing requirement for the first time at 31.2.s and then showed a tendency of deterioration. It met the requirement again at 58.2.s with the mixing density difference meeting the mixing criterion of 3‰.
Employing the standard k-ε turbulent model and slipping grid technique, distributions of velocity and dynamic pressure and mixing time was numerically investigated to research the gasoline flow features and mixing efficiency in a gasoline mixture tank with a rotary jet mixing (RJM) system installed at the bottom center. The simulation results showed that the RJM system can achieve fully circular stir without blind corner, reaching high mixing efficiency in the mixing process of gasoline from different refining line. The mixing density difference met the mixing requirement for the first time at 31.2.s and then showed a tendency of deterioration. It met the requirement again at 58.2.s with the mixing density difference meeting the mixing criterion of 3‰.
Reference Distance Estimator
Yanpeng Li
Computer Science , 2013,
Abstract: A theoretical study is presented for a simple linear classifier called reference distance estimator (RDE), which assigns the weight of each feature j as P(r|j)-P(r), where r is a reference feature relevant to the target class y. The analysis shows that if r performs better than random guess in predicting y and is conditionally independent with each feature j, the RDE will have the same classification performance as that from P(y|j)-P(y), a classifier trained with the gold standard y. Since the estimation of P(r|j)-P(r) does not require labeled data, under the assumption above, RDE trained with a large number of unlabeled examples would be close to that trained with infinite labeled examples. For the case the assumption does not hold, we theoretically analyze the factors that influence the closeness of the RDE to the perfect one under the assumption, and present an algorithm to select reference features and combine multiple RDEs from different reference features using both labeled and unlabeled data. The experimental results on 10 text classification tasks show that the semi-supervised learning method improves supervised methods using 5,000 labeled examples and 13 million unlabeled ones, and in many tasks, its performance is even close to a classifier trained with 13 million labeled examples. In addition, the bounds in the theorems provide good estimation of the classification performance and can be useful for new algorithm design.
Camping and quality of life  [PDF]
Frank H. Fu, Linxuan Guo, Yanpeng Zang
Open Journal of Preventive Medicine (OJPM) , 2013, DOI: 10.4236/ojpm.2013.33036
Abstract:

Attaining health and quality of life is universal among global citizens. Since its introduction by Dr. Halbert Dunn in 1962 the term wellness was used to reflect qualify of life and has been widely accepted and defined in the Western culture. In adapting this concept to the Chinese community, the components of adaptation and homeostasis should be considered in addition to physical, mental, social and health fitness. Camping is a common activity among the Western Culture which provides purposive leisure, social, education and therapeutic activities. It allows campers to escape from city life and enjoy Nature. In the Chinese community, the challenges remain to promote and develop camping to an attractive activity in the pursuit of quality of life and wellness. The present study would report the effects of selective camping programs on campers, the lifestyle management practices of Hong Kong residents and a profile of Hong Kong campers. The study was limited with data obtained from surveying 975 Hong Kong secondary school children from 11 - 18 years old using a questionnaire developed earlier [1]. Also, the case study on the effects of camping on anxiety was based on data collected from 130 campers who went to a 3-day camp.

Aerodynamics and Flight Dynamics of Free-Falling Ash Seeds  [PDF]
Rui Fang, Yanlai Zhang, Yanpeng Liu
World Journal of Engineering and Technology (WJET) , 2017, DOI: 10.4236/wjet.2017.54B012
Abstract:
Samaras or winged seeds spread themselves by wind. Ash seed, unlike other samaras, has a high aspect ratio wing which can generate enough lift force to slow down descent by rotating about the vertical axis and spinning around its wing span axis simultaneously. This unique kinematics and inherent fluid mechanism are definitely of great interest. Detailed kinematics of free falling ash seeds were measured using high-speed cameras, then corresponding aerodynamic forces and moments were calculated employing computational fluid dynamics. The results show that both rotating and spinning directions are in the same side and the spinning angular velocity is about 6 times of rotating speed. The terminal descending velocity and cone angles are similar to other samaras. Analysis of the forces and moments shows that the lift is enough to balance the weight and the vertical rotation results from a processional motion of total angular moment because the spin-cycle-averaged aer-odynamic moment is perpendicular to the total angular moment and can only change its direction but maintain its magnitude, which is very similar to a spinning top in processional motion except that the total angular moment of ash seed is not along the spin axis but almost normal to it. The flow structures show that both leading and trailing edge vortices contribute to lift generation and the spanwise spinning results in an augmentation of the lift, implying that ash seeds with high aspect ratio wing may evolve in a different way in utilizing fluid mechanisms to facilitate dispersal.
Why to Use self Assembled Metallic Nanoparticles Template for Metal Electrodeposition: Metallic Nanostructures with Controlled Morphologies and Adjustable Wetting Properties
Taleb A.,Yanpeng X.
Proceedings of the International Conference Nanomaterials : Applications and Properties , 2013,
Abstract: We investigated the benefits of using self assembled gold nanoparticles (Au NPs) template for metal electrodepositions. For short electrodeposition time, surface patterning was achieved and a well dense organized structure with nanometre resolution of metallic nanoparticles was prepared. For longer electrodeposition time, different morphologies were obtained. The mechanisms behind the formation of this morphology were analysed and discussed based on the influence of self-assembled Au NPs template in terms of thiol molecules diffusion and adsorption on metallic deposits. Furthermore adjustable wetting properties were obtained through the tuning of electrode-position time.
A Visible Watermarking Scheme in Spatial Domain Using HVS Model
Wenfei Zeng,Yanpeng Wu
Information Technology Journal , 2010,
Abstract: Most existing visible watermarking techniques only considering the host image characteristics and the visible watermark has low contrast. To achieve optimal balance between the visual quality and the visible watermark contrast, an image adaptive visible watermarking scheme in spatial domain is proposed by considering human visual system characteristics. Firstly, the scaling factor and the embedding factor for watermark insertion are calculated by combining both the host image features and the watermark image features (such as luminance and texture sensitivity). Secondly, the visible watermark is embedded into the host image by adjusting adaptively the scaling factor and the embedding factor. The visible watermark is adaptive to the host image due to the use of visual perception features. Extensive experimental results show that the watermarked image has good perceptible quality and high robustness against attempts of removal and the visible watermark has high contrast to the host image. On the average, the proposed scheme achieves at least 2.1 higher PSNR values than existing approaches.
Polarization Saturation in Strained Ferroelectrics
Yanpeng Yao,Huaxiang Fu
Physics , 2008,
Abstract: Using density-functional calculations we study the structure and polarization response of tetragonal PbTiO3, BaTiO3 and SrTiO3 in a strain regime that is previously overlooked. Different from common expectations, we find that the polarizations in all three substances saturate at large strains, demonstrating a universal phenomenon. The saturation is shown to originate from an unusual and strong electron-ion correlation that leads to cancellation between electronic and ionic polarizations. Our results shed new insight on the polarization properties, and reveal the existence of a fundamental limit to the strain-induced polarization enhancement.
Strain dependencies of energetic, structural, and polarization properties in tetragonal (PbTiO3)1/(SrTiO3)1 and (BaTiO3)1/(SrTiO3)1 superlattices: a comparative study with bulks
Yanpeng Yao,Huaxiang Fu
Physics , 2010,
Abstract: First-principles density functional calculations are performed to investigate the interplay between inplane strains and interface effects in 1by1 PbTiO3/SrTiO3 and BaTiO3/SrTiO3 superlattices of tetragonal symmetry. One particular emphasis of this study is to conduct side-by-side comparisons on various ferroelectric properties in short-period superlattices and in constituent bulk materials, which turns out to be rather useful in terms of obtaining valuable insight into the different physics when ferroelectric bulks form superlattices. The various properties that are studied in this work include the equilibrium structure, strain dependence of mixing energy, microscopic ferroelectric off-center displacements, macroscopic polarization, piezoelectric coeffcients, effective charges, and the recently formulated k-dependent polarization dispersion structure. The details of our findings are rather lengthy, and are summarized in Sec. IV.
The structure of electronic polarization and its strain dependence
Yanpeng Yao,Huaxiang Fu
Physics , 2008, DOI: 10.1103/PhysRevB.79.014103
Abstract: The $\phi(\kpp)\sim \kpp$ relation is called polarization structure. By density functional calculations, we study the polarization structure in ferroelectric perovskite PbTiO$_3$, revealing (1) the $\kpp$ point that contributes most to the electronic polarization, (2) the magnitude of bandwidth, and (3) subtle curvature of polarization dispersion. We also investigate how polarization structure in PbTiO$_3$ is modified by compressive inplane strains. The bandwidth of polarization dispersion in PbTiO$_3$ is shown to exhibit an unusual decline, though the total polarization is enhanced. As another outcome of this study, we formulate an analytical scheme for the purpose of identifying what determine the polarization structure at arbitrary $\kpp$ points by means of Wannier functions. We find that $\phi(\kpp)$ is determined by two competing factors: one is the overlaps between neighboring Wannier functions within the plane {\it perpendicular} to the polarization direction, and the other is the localization length {\it parallel} to the polarization direction. Inplane strain increases the former while decreases the latter, causing interesting non-monotonous effects on polarization structure. Finally, polarization dispersion in another paradigm ferroelectric BaTiO$_3$ is discussed and compared with that of PbTiO$_3$.
Influence of rotational instability on the polarization structure of SrTiO3
Yanpeng Yao,Huaxiang Fu
Physics , 2010, DOI: 10.1103/PhysRevB.82.174119
Abstract: The k-space polarization structure and its strain response in SrTiO3 with rotational instability are studied using a combination of first-principles density functional calculations, modern theory of polarization, and analytic Wannier-function formulation. (1) As one outcome of this study, we rigorously prove-both numerically and analytically-that folding effect exists in polarization structure. (2) After eliminating the folding effect, we find that the polarization structure for SrTiO3 with rotational instability is still considerably different from that for non-rotational SrTiO3, revealing that polarization structure is sensitive to structure distortion of oxygen-octahedra rotation and promises to be an effective tool for studying material properties. (3) Furthermore, from polarization structure we determine the microscopic Wannier-function interactions in SrTiO3. These interactions are found to vary significantly with and without oxygen-octahedra rotation.
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