Understanding the nanoscale local buckling behavior of vertically aligned MWCNT arrays with van der Waals interactions

Li, Yupeng,Kim, Hyung-ick,Wei, Bingqing,Kang, Junmo,Choi, Jae-boong,Nam, Jae-Do,Suhr, Jonghwan The Royal Society of Chemistry 2015 Nanoscale Vol.7 No.34

Fabrication of Hollow Polymer Microchannels Using the MIMIC Technique with Subsequent Heat Treatment

Weiren Li,Wenqiang Xing,Fengzhou Zhao,Lichun Zhang,Yupeng Huang,Jinxiu Li,Linwei Zhu,Zheng Xu,Dengying Zhang 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.8

The hollow polymer microchannels with different shapes and dimensions have been fabricated by the MIMIC method and the heating process for the first time. The smallest cross-sectional dimensions of hollow polymer microchannels were about 2.6 μm in the vertical direction and 3.5 μm in the horizontal direction. The length of hollow polymer microchannels increased parabolically with the heating temperature in the range of 30–135 °C. And the influence of the PDMS mold crosssectional areas on the length of the microchannels was invetigated. Furthermore, the forming mechanism of hollow polymer microchannels was disscussed in detail. This technique provides a cheap, simple and controllable way for the preparation of microchannels.

The Damage Criterion Affecting Life Prediction of Fiber-Reinforced Al–Li Alloy Laminates Under Spectrum Loading

Meng Weiying,Li Yupeng,Zhang Xiaochen,Shi Huaitao,Zhang Yu,Lv Xiao 한국항공우주학회 2020 International Journal of Aeronautical and Space Sc Vol.21 No.4

Fiber metal laminates, as the new generation of aircraft structural materials, are widely concerned by material researcher. This paper presents a study on the life prediction problems of fiber-reinforced Al–Li alloy laminates under spectrum loading by applying the cumulative damage and residual strength models. Firstly, fatigue life performance of the laminate materials is tested under different loading cases. Then, the most advanced damage accumulation and residual strength models are summarized, which is applied to composite laminates. Some models are directly abandoned because the data needed for fitting model cannot be obtained by this experiment or the model formulation is prevented directly to the application for the spectrum blocks with free loading. Meanwhile, a cumulative damage model considering residual strength is modified accordingly based on the characteristics of life prediction under spectrum loading. To study the impacts of these models on the fatigue life prediction for fiber reinforced Al–Li alloy laminate under spectrum loading, the predicted accuracy of these models will be compared by applying them to life prediction problems of 2/1 laminate and 3/2 laminate. Results show that compared with other models, modified model improves the prediction accuracy especially for 3/2 laminate.

Changes of Shoulder, Elbow, and Wrist Stiffness Matrix Post Stroke

Li-Qun Zhang,Jongsang Son,Hyung-Soon Park,Sang Hoon Kang,Yunju Lee,Yupeng Ren IEEE 2017 IEEE transactions on neural systems and rehabilita Vol.25 No.7

<P>Stroke affects multiple joints in the arm with stereotypical patterns of arm deformity involving the shoulder, elbow, wrist, and hand and with disrupted coordination of multiple joints in active movements. However, there is a lack of systematicmethods to evaluatemulti-joints and multi-degree of freedoms (DOF) neuro-mechanical changes, especially for complex systemswith three ormore joints/ DOFs involved. This paper used a novel systematic method to characterize dynamics and control of the shoulder, elbow, and wrist of the human arm individually and simultaneously, including the couplings across themultiple joints during controlled movements. A novel method was developed to decompose the complex system into manageable single-joint level for more reliable characterizations. The method was used in clinical studies to characterize the multi-joint changes associated with spastic impaired arm of 11 patients post stroke and 12 healthy controls. It was found that stroke survivors showed not only increased stiffness at the individual joints locally but also significantly higher couplings across the joints. The relative increases in couplings are often higher than that of the local joint stiffness. The multi-joint characterization provided a tool to characterize impairment of individual patients, which would allow more focused impairment-specific treatment. In general, the decomposition method can be used for even more complex systems, making characterization of intractable system dynamics of three or more joints/DOFs manageable.</P>

Novel Hierarchical TiO2/C Nanocomposite with Enhanced Photocatalytic Performance

Yupeng Gao,Hao Chen,Aiguo Zhou,Zhengyang Li,Fanfan Liu,Qianku Hu,Libo Wang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.5

"Hierarchical TiO2 /carbon nanocomposites were synthesized by oxidation of two-dimensional(2D) Ti3C2 nanosheets at different temperatures. Crystal structures and morphologies of the obtained samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Raman spectroscopy. The results show that 2D Ti3C2 nanosheets are partially oxidized to form a novel hierarchical nanostructure which is composed of carbon nanosheets and TiO2 nanoparticles. With the calcination temperature increasing, the crystal structure of TiO2 nanoparticles changes from anatase to rutile and the hierarchical structure was gradually destroyed. The photodegradation results reveal that the samples obtained at 200℃ and 285℃ show much better photocatalytic properties than P25. And meanwhile the photocatalytic property will become worse with the increase in calcinations temperature."

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.

Coactosin-like protein 1 inhibits neuronal migration during mouse corticogenesis

Guohong Li,Yupeng Yin,Jiong Chen,Yanle Fan,Juhong Ma,Yingxue Huang,Chen Chen,Pengxiu Dai,Shulin Chen,Shanting Zhao 대한수의학회 2018 Journal of Veterinary Science Vol.19 No.1

Coactosin-like protein 1 (Cotl1), a member of the actin-depolymerizing factor (ADF)/cofilin family, was first purified from a soluble fraction of Dictyostelium discoideum cells. Neuronal migration requires cytoskeletal remodeling and actin regulation. Although Cotl1 strongly binds to F-actin, the role of Cotl1 in neuronal migration remains undescribed. In this study, we revealed that Cotl1 overexpression impaired migration of both early- and late-born neurons during mouse corticogenesis. Moreover, Cotl1 overexpression delayed, rather than blocked, neuronal migration in late-born neurons. Cotl1 expression disturbed the morphology of migrating neurons, lengthening the leading processes. This study is the first to investigate the function of Cotl1, and the results indicate that Cotl1 is involved in the regulation of neuronal migration and morphogenesis.

Separating machining errors of S-shaped samples based on the comprehensive error field of five-axis machine tools

Shi Wu,Yupeng Wang,Xian-li Liu,Zhengdong Fan,Tai Yu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.1

In the present study, a new method is proposed to separate machining errors of a 5-axis machine tool with a double turntable. Moreover, a high-precision compensation model is established to calculate machining errors of thin-walled parts in a 5-axis machine tool. In this regard, a comprehensive error model of the S-shaped sample part considering geometric, thermal, and machining errors is established. Then based on the homogeneous transformation matrix, the geometric error models of translational axes and the A and C axes of the rotation axis are established. Accordingly, geometric errors of each motion axes are identified and measured. Meanwhile, the thermal error of the spindle is measured, and the thermal error model of the machine tool along X/Y/Z directions is established using the multiple linear regression method. Finally, the S-shaped sample is processed and the on-machine measurement of the sample surface is carried out. Based on the obtained machining error from the separation method, the distribution of the total surface error at different curvatures of the S-shaped sample is analyzed, and the distributions of geometric and thermal errors of the machine tool are obtained. It is found that when the geometric and thermal errors of the machine tool are compensated, the measured machining error of each point of the S-shaped sample can be reduced by 10-15 μm compared with that before compensation.

Improvement in Offaxis Neuromuscular Control Under Slippery Conditions Following Six-Week Pivoting Leg Neuromuscular Training

Lee, Song Joo,Ren, Yupeng,Press, Joel M.,Lee, Jungwha,Zhang, Li-Qun IEEE 2017 IEEE transactions on neural systems and rehabilita Vol.25 No.11

<P>Knee injuries are usually associated with offaxis loadings in the transverse and frontal planes. Thus, improvement of lower limb offaxis neuromuscular control is important in knee injury prevention and post-injury rehabilitation. The goal of this paper was to investigate the effects of six-week pivoting offaxis intensity adjustable neuromuscular control training (POINT) using a custom-made offaxis elliptical trainer on lower limb offaxis neuromuscular control performance in trained and untrained functional tasks under slippery conditions. Twenty-six subjects participated in 18 sessions of POINT (three sessions per week for six weeks) and 25 subjects served as controls who did a regular workout. Offaxis neuromuscular control performance measures in terms of pivoting instability, sliding instability, and time-to-peak offaxis EMG entropy were evaluated on both groups under slippery conditions including a trained free pivoting task and untrained free sliding task and free pivoting and sliding task. Compared with the control group, the training group significantly decreased pivoting instability and the time-to-peak offaxis EMG entropy in lower limb muscles, indicating improvement in offaxis neuromuscular control performance. Furthermore, the training group showed reduced pivoting instability and sliding instability during the untrained free pivoting and sliding task. This paper may help us develop more focused and effective offaxis training programs to reduce knee injuries associated with offaxis loadings.</P>

Tilting Control of Rotor Suspended by Complex Magnetic Bearings with Coupling Torques

Jiqiang Tang,Min Zhang,Yupeng Li,Jinji Sun 한국자기학회 2023 Journal of Magnetics Vol.28 No.1

For a novel Vernier-gimballing magnetically suspended flywheel (Vernier-gimballing MSFW) with conical magnetic bearing (MB) and Lorentz MB, the rotor’s dynamic model is constructed based on the characteristics of both coupling torque generated by conical MB and nonlinear titling torques generated by Lorentz MB. To make the high-speeding rotor tilt precisely and fast to output large moment, the Vernier-gimballing control method based on the extended state observer (ESO) combined with feedback linearization is presented originally considering torques’ complex nonlinearities, and the sliding mode control (SMC) with ESO is designed to improve the robustness of the closed-loop system. Simulations and experimental tests to verify the rightness and validity of SMC with ESO have been done and all research results indicate that the rotor can track the tilting signal faster and more accurately than classic SMC to output high precision moment.