Experimental study on the influence of Reynolds number and roll angle on train aerodynamics

Zhixiang Huang,Wenhui Li,Tanghong Liu,Li Chen 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.35 No.2

When the rolling stocks run on the curve, the external rail has to be lifted to a certain level to balance the centrifugal force acting on the train body. Under such a situation, passengers may feel uncomfortable, and the slanted vehicle has the potential overturning risks at high speed. This paper conducted a wind tunnel test in an annular wind tunnel with φ=3.2 m based on a 1/20th scaled high-speed train (HST) model. The sensitivity of Reynolds effects ranging from Re = 0.37×106 to Re = 1.45×106 was tested based on the incoming wind from U=30 m/s to U=113 m/s. The wind speed covers the range from incompressible to compressible. The impact of roll angle ranging from γ=0° to γ=4° on train aerodynamics was tested. In addition, the boundary layer development was also analyzed under different wind speeds. The results indicate that drag and lift aerodynamic coefficients gradually stabilized and converged over U=70 m/s, which could be regeared as the self-similarity region. Similarly, the thickness of the boundary layer on the floor gradually decreased with the wind speed increase, and little changed over U=80 m/s. The rolling moment of the head and tail cars increased with the roll angle from γ=0° to γ=4°. However, the potential overturning risks of the head car are higher than the tail car with the increase of the roll angle. This study is significant in providing a reference for the overturning assessment of HST.

Graded-Three-Dimensional Cell-Encapsulating Hydrogel as a Potential Biologic Scaffold for Disc Tissue Engineering

Li Zhixiang,Zhang Yiwen,Zhao Yupeng,Gao Xubin,Zhu Zhonglian,Mao Yingji,Qian Taibao 한국조직공학과 재생의학회 2022 조직공학과 재생의학 Vol.19 No.5

BACKGROUND: Intervertebral disk (IVD) degeneration, which can cause lower back pain, is a major predisposing factor for disability and can be managed through multiple approaches. However, there is no satisfactory strategy currently available to reconstruct and recover the natural properties of IVDs after degeneration. As tissue engineering develops, scaffolds with embedded cell cultures have proved critical for the successful regeneration of IVDs. METHODS: In this study, an integrated scaffold for IVD replacement was developed. Through scanning electron microscopy and other mechanical measurements, we characterized the physical properties of different hydrogels. In addition, we simulated the physiological structure of natural IVDs. Nucleus pulposus (NP) cells and annulus fibrosusderived stem cells (AFSCs) were seeded in gelatin methacrylate (GelMA) hydrogel at different concentrations to evaluate cell viability and matrix expression. RESULTS: It was found that different concentrations of GelMA hydrogel can provide a suitable environment for cell survival. However, hydrogels with different mechanical properties influence cell adhesion and extracellular matrix component type I collagen, type II collagen, and aggrecan expression. CONCLUSION: This tissue-engineered IVD implant had a similar structure and function as the native IVD, with the inner area mimicking the NP tissue and the outer area mimicking the stratified annulus fibrosus tissue. The new integrated scaffold demonstrated a good simulation of disc structure. The preparation of efficient and regeneration-promoting tissueengineered scaffolds is an important issue that needs to be explored in the future. It is hoped that this work will provide new ideas and methods for the further construction of functional tissue replacement discs.

Wideband Differentially Fed Circularly Polarized Slotted Patch Antenna with a Large Beamwidth

Li, Wen,Xue, Wei,Li, Yingsong,Kwok L. Chung,Zhixiang Huang 한국전자파학회 2023 Journal of Electromagnetic Engineering and Science Vol.23 No.6

A wideband differentially fed circularly polarized (CP) antenna featuring a slotted patch design with a large beamwidth is presented. The final design of the differentially fed CP antenna, aimed at achieving high gain and a wide axial ratio (AR) bandwidth, involves coupling a differential bending dipole antenna to the slotted patch in the same plane. The presented differentially fed CP antenna demonstrates characteristics of a large AR beamwidth, as verified by simulation and experiment. The measured AR beamwidths of 132.3° in the xoz plane (phi = 0°) and 116.2° in the yoz plane (phi = 90°) are realized at 5.5 GHz. The measured result exhibits broadband performance with a -10-dB impedance bandwidth of 78.8% (3.81–8.76 GHz), a 3-dB AR bandwidth of 36.7% (4.78–6.93 GHz), and a maximum gain of 10.2 dBic.

Effects of cyclic loads on viscoelastic behavior of brain tissue on the implanting trajectory of STN-DBS

Zhixiang Huang,Chunyang Pan,Panling Huang,Jun Zhou,Xueen Li 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.4

During deep brain stimulation of the sub-thalamic nucleus (STN-DBS), frequently adjusting the position of the cannula may lead to changes in tissue viscoelasticity. To investigate the mechanical properties of tissue on implant path at repeated loads, three cyclic tension and relaxation tests were carried out at 10 % and 20 % strains. Results indicated that white matter was about 25 %-140 % stiffer than gray matter. Within 20 % strain, the natural viscoelasticity of tissue was not affected by the repeated tension. Whereas at 20 % strain, irreversible internal structure rearrangements occurred at the first relaxation due to the persistent strain action, and almost 60 % of the attenuation modulus generated in the initial 5 s of the process, which leads to a softer transformation of the tissue. Further simulated puncture experiments revealed that an irreversible depression occurred when the cerebral hemisphere was subjected to a constant pressure of cannula for 5 s.

Development of Array-based Technology for Detection of HAV Using Gold-DNA Probes

Wan, Zhixiang,Wang, Yefu,Li, Shawn Shun-Cheng,Duan, Lianlian,Zhai, Jianxin Korean Society for Biochemistry and Molecular Biol 2005 Journal of biochemistry and molecular biology Vol.38 No.4

A sensitive method for detection of Hepatitis A virus (HAV) by utilizing gold-DNA probe on an array was developed. Amino- modified oligodeoxynucleotides at the 5' position were arrayed on an activated glass surface to function as capture probes. Sandwich hybridization occurred among capture probes, the HAV amplicon, and gold nanoparticle-supported oligonucleotide probes. After a silver enhancement step, signals were detected by a standard flatbed scanner or just by naked eyes. As little as 100 fM of HAV amplicon could be detected on the array. Therefore, the array technology is an alternative to be applied in detection of HAV due to its low-cost and high-sensitivity.

Low Frequency Current Ripple Mitigation of Two Stage Three-Phase PEMFC Generation Systems

Deng, Huiwen,Li, Qi,Liu, Zhixiang,Li, Lun,Chen, Weirong The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

This paper presents a two stage three-phase proton exchange membrane fuel cell (PEMFC) generation system. When the system is connected to a three-phase load, it is very sensitive to the characteristics and type of the load. Especially unbalanced three-phase loads, which result in a pulsating power that is twice the output frequency at the inverter output, and cause the dc-link to generate low frequency ripples. This penetrates to the fuel cell side through the front-end dc-dc converter, which makes the fuel cell work in an unsafe condition and degrades its lifespan. In this paper, the generation and propagation mechanism of low frequency ripple is analyzed and its impact on fuel cells is presented based on the PEMFC output characteristics model. Then a novel method to evaluate low frequency current ripple control capability is investigated. Moreover, a control scheme with bandpass filter inserted into the current feed-forward path, and ripple duty ratio compensation based on current mode control with notch filter is also proposed to achieve low frequency ripple suppression and dynamic characteristics improvement during load transients. Finally, different control methods are verified and compared by simulation and experimental results.

Global Attractivity and Oscillations in a Nonlinear Impulsive Parabolic Equation with Delay

Wang, Xiao,Li, Zhixiang Department of Mathematics 2008 Kyungpook mathematical journal Vol.48 No.4

Global attractivity and oscillatory behavior of the following nonlinear impulsive parabolic differential equation which is a general form of many population models $$\array{\{{{\frac {{\partial}u(t,x)}{{\partial}t}=\Delta}u(t,x)-{\delta}u(t,x)+f(u(t-\tau,x)),\;t{\neq}t_k,\\u(t^+_k,x)-u(t_k,x)=g_k(u(t_k,x)),\;k{\in}I_\infty,}\;\;\;\;\;\;\;\;(*)$$ are considered. Some new sufficient conditions for global attractivity and oscillation of the solutions of (*) with Neumann boundary condition are established. These results no only are true but also improve and complement existing results for (*) without diffusion or impulses. Moreover, when these results are applied to the Nicholson's blowflies model and the model of Hematopoiesis, some new results are obtained.

pH/Temperature Responsive Curcumin-Loaded Micelle Nanoparticles Promote Functional Repair after Spinal Cord Injury in Rats via Modulation of Inflammation

Qian Taibao,Li Zhixiang,Shang Lijun,Huang Sutao,Li Guanglin,Zheng Weiwei,Mao Yingji 한국조직공학과 재생의학회 2023 조직공학과 재생의학 Vol.20 No.6

BACKGROUND: The formation of an inhibitory inflammatory microenvironment after spinal cord injury (SCI) remains a great challenge for nerve regeneration. The poor local microenvironment exacerbates nerve cell death; therefore, the reconstruction of a favorable microenvironment through small-molecule drugs is a promising strategy for promoting nerve regeneration. METHODS: In the present study, we synthesized curcumin-loaded micelle nanoparticles (Cur-NPs) to increase curcumin bioavailability and analyzed the physical and chemical properties of Cur-NPs by characterization experiments. We established an in vivo SCI model in rats and examined the ability of hind limb motor recovery using Basso–Beattie– Bresnahan scoring and hind limb trajectory assays. We also analyzed neural regeneration after SCI using immunofluorescence staining. RESULTS: The nanoparticles achieved the intelligent responsive release of curcumin while improving curcumin bioavailability. Most importantly, the released curcumin attenuated local inflammation by modulating the polarization of macrophages from an M1 pro-inflammatory phenotype to an M2 anti-inflammatory phenotype. M2-type macrophages can promote cell differentiation, proliferation, matrix secretion, and reorganization by secreting or expressing pro-repair cytokines to reduce the inflammatory response. The enhanced inflammatory microenvironment supported neuronal regeneration, nerve remyelination, and reduced scar formation. These effects facilitated functional repair in rats, mainly in the form of improved hindlimb movements. CONCLUSION: Here, we synthesized pH/temperature dual-sensitive Cur-NPs. While improving the bioavailability of the drug, they were also able to achieve a smart responsive release in the inflammatory microenvironment that develops after SCI. The Cur-NPs promoted the regeneration and functional recovery of nerves after SCI through anti-inflammatory effects, providing a promising strategy for the repair of SCIs.

Second Order Impulsive Neutral Functional Differential Inclusions

Liu, Yicheng,Li, Zhixiang Department of Mathematics 2008 Kyungpook mathematical journal Vol.48 No.1

In this paper, we investigate the existence of solutions of second order impulsive neutral functional differential inclusions which the nonlinearity F admits convex and non-convex values. Some results under weaker conditions are presented. Our results extend previous ones. The methods rely on a fixed point theorem for condensing multivalued maps and Schaefer's fixed point theorem combined with lower semi-continuous multivalued operators with decomposable values.

Biomimetic Total Synthesis of Paeoveitol

Zhang, Yuhan,Guo, Yonghong,Li, Zhongle,Xie, Zhixiang American Chemical Society 2016 ORGANIC LETTERS Vol.18 No.18

<P>A highly stereocontrolled synthesis of paeoveitol has been developed in 26% yield, in 7 steps from commercially available materials. The synthetic strategy was inspired primarily by the biogenetic hypothesis and was enabled by hetero-Diels–Alder cycloaddition to construct the target molecular framework.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/orlef7/2016/orlef7.2016.18.issue-18/acs.orglett.6b02228/production/images/medium/ol-2016-02228p_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ol6b02228'>ACS Electronic Supporting Info</A></P>