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1,629 results on '"Wang, Longfei"'

5. Flow Dynamics of a Dodecane Jet in Oxygen Crossflow at Supercritical Pressures

Author

Ding, Siyu, Li, Jiabin, Wang, Longfei, Ni, Chenxu, and Wang, Xingjian

Subjects
Physics - Fluid Dynamics
Abstract

In advanced aero-propulsion engines, kerosene is often injected into the combustor at supercritical pressures, where flow dynamics is distinct from the subcritical counterpart. Large-eddy simulation combined with real-fluid thermodynamics and transport theories of a N-dodecane jet in oxygen crossflow at supercritical pressures is presented. Liquid dodecane at 600 K is injected into a supercritical oxygen environment at 700 K at different supercritical pressures and jet-to-crossflow momentum flux ratios (J). Various vortical structures are discussed in detail. The results shown that, with the same jet-to-crossflow velocity ratio of 0.75, the upstream shear layer (USL) is absolutely unstable at 6.0 MPa (J = 7.1) and convectively unstable at 3.0 MPa (J = 13.2). This trend is consistent with the empirical criterion for the stability characteristics of a jet in crossflow at subcritical pressures (Jcr = 10). While decreasing J to 7.1 at 3.0 MPa, however, the dominant Strouhal number of the USL varies along the upstream jet trajectory, and the USL becomes convectively unstable. Such abnormal change in stability behavior can be attributed to the real-fluid effect induced by strong density stratification at pressure of 3.0 MPa, under which a point of inflection in the upstream mixing layer renders large density gradient and tends to stabilize the USL. The stability behavior with varying pressure and J is further corroborated by linear stability analysis. The analysis of spatial mixing deficiencies reveals that the mixing efficiency is enhanced at a higher jet-to-crossflow momentum flux ratio., Comment: 1. The citations "Cortelezzi & Karagozian 2001; Yang & Wang 2005" in Page2 were wrong, which are not "compressible". This would mislead the readers. 2. The Reynolds number announced in Page7 was wrong by an order of magnitude

Published
2023

9. Analysis of systemic reactions during house dust mite subcutaneous immunotherapy in children with allergic rhinitis

Author

WANG Xiancheng, WANG Longfei, ZHENG Xiaoshun, XIAO Xiaoxiong, LI Lihao, MO Lihua

Subjects
allergic rhinitis, dust mite, subcutaneous immunotherapy, systemic reaction, children, Medicine
Abstract

Objective To observe the systemic reactions （SRs） associated with subcutaneous immunotherapy （SCIT） using dust mite allergen and to analyze potential risk factors. Methods The occurrence of SRs among 230 patients with allergic rhinitis （AR） who received house dust mite SCIT from December 2019 to December 2022 was retrospectively analyzed， and related risk factors were identified. Results A total of 5 422 injections were given to 230 patients， with an SRs incidence rate of 2.4% per injection and 20.0% per patient. Most SRs were grade I （51.9%）， and no fatal SRs occurred. Symptoms primarily affected the respiratory system for 111 times （84.7%）. Elevated peripheral blood eosinophil count （OR （95% CI）=6.02 （1.76， 20.60）， P = 0.004） and high levels of house dust mite-specific IgE （OR （95% CI）=1.01 （1.00， 1.01）， P = 0.016） were identified as risk factors for SRs， respectively. Conclusions Children with AR allergic to dust mites may experience SRs during SCIT with standardized dust mite allergen preparations， whereas the overall safety of SCIT is good. High eosinophil count and high levels of house dust mite-specific IgE are risk factors for SRs during SCIT.

Published
2024
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33. Inverse Kinematics and Dexterous Workspace Formulation for 2-Segment Continuum Robots with Inextensible Segments

Author

Wang, Yifan, Wu, Zhonghao, Wang, Longfei, Feng, Bo, and Xu, Kai

Subjects
Computer Science - Robotics
Abstract

The inverse kinematics (IK) problem of continuum robots has been investigated in depth in the past decades. Under the constant-curvature bending assumption, closed-form IK solution has been obtained for continuum robots with variable segment lengths. Attempting to close the gap towards a complete solution, this paper presents an efficient solution for the IK problem of 2-segment continuum robots with one or two inextensible segments (a.k.a, constant segment lengths). Via representing the robot's shape as piecewise line segments, the configuration variables are separated from the IK formulation such that solving a one-variable nonlinear equation leads to the solution of the entire IK problem. Furthermore, an in-depth investigation of the boundaries of the dexterous workspace of the end effector caused by the configuration variables limits as well as the angular velocity singularities of the continuum robots was established. This dexterous workspace formulation, which is derived for the first time to the best of the authors' knowledge, is particularly useful to find the closest orientation to a target pose when the target orientation is out of the dexterous workspace. In the comparative simulation studies between the proposed method and the Jacobian-based IK method involving 500,000 cases, the proposed variable separation method solved 100% of the IK problems with much higher computational efficiency., Comment: Submitted to IEEE Robotics and Automation Letters

Published
2021

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