Thermo-electro-mechanical vibration and buckling analysis of a functionally graded piezoelectric porous cylindrical microshell

Zhipeng Lyu,Wenguang Liu,Chao Liu,Yuhang Zhang,Mengxiang Fang 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.10

In this paper, the vibration and buckling behavior of a functionally graded piezoelectric porous cylindrical microshell under thermo-electro-mechanical loads are explored on the basis of modified couple stress theory and higher-order shear deformation theory. First, the model of a functionally graded piezoelectric porous cylindrical microshell composed of piezoelectric materials with gradient change in the thickness direction was described. Second, the governing equations of the microshell were derived by Hamilton's principle and Maxwell equation. Third, the modal frequency and buckling equations of the microshell with simply supported ends were obtained on the basis of harmonic trigonometric functions. Finally, the effects of parameters on the modal frequency and buckling behavior were carried out by case studies. The results show that the modal frequency of the microshell can be adjusted by changing the porosity volume fraction, power index, applied voltage, axial load and geometric dimensions. It is also found that the vibration of the microshell is suppressed by positive voltage and axial compression but is strengthened by negative voltage and axial tension, and the material length scale parameter increases stiffness. In addition, the effects of applied voltage and axial load on the buckling behavior are larger than those of temperature. Results can be used to guide the design and application of piezoelectric devices.

Mixing matrix estimation method for dual‐channel time‐frequency overlapped signals based on interval probability

Zhipeng Liu,Lichun Li,Ziru Zheng 한국전자통신연구원 2019 ETRI Journal Vol.41 No.5

For dual‐channel time‐frequency (TF) overlapped signals with low sparsity in underdetermined blind source separation (UBSS), this paper proposes an effective method based on interval probability to estimate and expand the types of mixing matrices. First, the detection of TF single‐source points (TF‐SSP) is used to improve the TF sparsity of each source. For more distinguishability, as the ratios of the coefficients from different columns of the mixing matrix are close, a local peak‐detection mechanism based on interval probability (LPIP) is proposed. LPIP utilizes uniform subintervals to optimize and classify the TF coefficient ratios of the detected TF‐SSP effectively in the case of a high level of TF overlap among sources and reduces the TF interference points and redundant signal features greatly to enhance the estimation accuracy. The simulation results show that under both noiseless and noisy cases, the proposed method performs better than the selected mainstream traditional methods, has good robustness, and has low algorithm complexity.

The Dynamic Influence Graph Model on Mobile Datasets

Zhipeng Liu,Dechang Pi,Yehong Wu 보안공학연구지원센터 2015 International Journal of Database Theory and Appli Vol.8 No.5

With the rapid development of mobile technologies, more and more people are equipped with smartphones. It is possible for scientists to collect and analyze mobile data efficiently. Mobile data contain rich semantic as well as topological information. Rich information can be inferred from these data such as social influence among different nodes in mobile social network. However, it is difficult to estimate the strength of social influence due to the characteristics of inherent dynamic and large scale of mobile social network. In this paper, a Dynamic Influence Graph (DIG) model is proposed which utilizes temporal information in a topological perspective, and an efficient algorithm is proposed based on the DIG model. The proposed algorithm can calculate social influence between any two nodes in a given mobile social network stream segment, and takes edge weights, node connectivity and temporal information into consideration. Experimental results with a real mobile social network dataset show that the proposed approach can infer social influence and achieve a-state-of-the-art accuracy (82-86%) efficiently and automatically.

Effective Separation Method for Single-Channel Time-Frequency Overlapped Signals Based on Improved Empirical Wavelet Transform

( Zhipeng Liu ),( Lichun Li ),( Huiqi Li ),( Chang Liu ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.5

To improve the separation performance of time-frequency overlapped radar and communication signals from a single channel, this paper proposes an effective separation method based on an improved empirical wavelet transform (EWT) that introduces a fast boundary detection mechanism. The fast boundary detection mechanism can be regarded as a process of searching, difference optimization, and continuity detection of the important local minima in the Fourier spectrum that enables determination of the sub-band boundary and thus allows multiple signal components to be distinguished. An orthogonal empirical wavelet filter bank that was designed for signal adaptive reconstruction is then used to separate the input time-frequency overlapped signals. The experimental results show that if two source components are completely overlapped within the time domain and the spectrum overlap ratio is less than 60%, the average separation performance is improved by approximately 32.3% when compared with the classic EWT; the proposed method also improves the suitability for multiple frequency shift keying (MFSK) and reduces the algorithm complexity.

A stochastic finite element method for dynamic analysis of bridge structures under moving loads

Xiang Liu,Lizhong Jiang,Ping Xiang,Zhipeng Lai,Yuntai Zhang,Lili Liu 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.82 No.1

In structural engineering, the material properties of the structures such as elastic modulus, shear modulus, density, and size may not be deterministic and may vary at different locations. The dynamic response analysis of such structures may need to consider these properties as stochastic. This paper introduces a stochastic finite element method (SFEM) approach to analyze moving loads problems. Firstly, Karhunen-Loéve expansion (KLE) is applied for expressing the stochastic field of material properties. Then the mathematical expression of the random field is substituted into the finite element model to formulate the corresponding random matrix. Finally, the statistical moment of the dynamic response is calculated by the point estimation method (PEM). The accuracy and efficiency of the dynamic response obtained from the KLE-PEM are demonstrated by the example of a moving load passing through a simply supported Euler-Bernoulli beam, in which the material properties (including elastic modulus and density) are considered as random fields. The results from the KLE-PEM are compared with those from the Monte Carlo simulation. The results demonstrate that the proposed method of KLE-PEM has high accuracy and efficiency. By using the proposed SFEM, the random vertical deflection of a high-speed railway (HSR) bridge is analyzed by considering the random fields of material properties under the moving load of a train.

Increased Expression of Heat Shock Protein 72 Protects Renal Proximal Tubular Cells from Gentamicin-induced Injury

Li Liu,Zhipeng Wang,Linna Liu,Yuhua Ran,Rong Zhang,Qibing Mei 대한의학회 2006 Journal of Korean medical science Vol.21 No.5

Live Media Streaming in VANETs using Traffic Flow

Shuoping Wang,Zhipeng Wang,Jun Liu,Honghao Gao,Meng Kuai 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.1

Multimedia streaming is a trend in VANETs infotainment service with establishment of infrastructure and communication standards. This paper considers the scenario of live multimedia streaming multicast to vehicles. We propose the relay selection scheme to deliver media streaming with stable link to improve QoS (quality of service). Through evaluation, our proposed scheme is able to have video delivered with a satisfying delay and acceptable loss ratio.

Decoupled SVPWM for Five-Phase Permanent Magnet Machines with Trapezoidal Back-EMF

Zhipeng Lin,Guohai Liu,Wenxiang Zhao,Qian Chen 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5

This paper presents a novel space vector pulse-width modulation (SVPWM) to synthesize an arbitrary non-sinusoidal phase voltage. The key of the proposed method is that the switching vectors used to comprise the reference vectors in the α₁-β₁ frame and the α₃-β₃ frame are decoupled. In the α₁-β₁ frame, the reference vector is comprised by near two large vectors. The corresponding vector comprised by the two vectors in the α₃-β₃ frame is considered as a disturbance, which is restrained by close-loop control. In the α₃-β₃ frame, there are two methods to comprise the reference vector. Method I is a near two middle vectors method. Method II uses near four vectors (two middle and two little vectors). The proposed SVPWM using decoupled switching vectors can guarantee a maximum modulation index in the α₁-β₁ frame. The effectiveness of the proposed method is verified by simulated and experimental results under various operation conditions.

Efficiently targeted therapy of glioblastoma xenograft via multifunctional biomimetic nanodrugs

Zhipeng Yao,Xiaochun Jiang,Hong Yao,Yafeng Wu,Fan Zhang,Cheng Wang,Chenxue Qi,Chenhui Zhao,Zeyu Wu,Min Qi,Jia Zhang,Xiaoxiang Cao,Zhichun Wang,Fei Wu,Chengyun Yao,Songqin Liu,Shizhang Ling,Hongping Xi 한국생체재료학회 2022 생체재료학회지 Vol.26 No.4

Background: Glioblastoma multiforme (GBM) is a fatal malignant primary brain tumor in adults. The therapeutic efficacy of chemotherapeutic drugs is limited due to the blood-brain barrier (BBB), poor drug targeting, and short biological half-lives. Multifunctional biomimetic nanodrugs have great potential to overcome these limitations of chemotherapeutic drugs. Methods: We synthesized and characterized a biomimetic nanodrug CMS/PEG-DOX-M. The CMS/PEG-DOX-M effectively and rapidly released DOX in U87 MG cells. Cell proliferation and apoptosis assays were examined by the MTT and TUNEL assays. The penetration of nanodrugs through the BBB and anti-tumor efficacy were investigated in the orthotopic glioblastoma xenograft models. Results: We showed that CMS/PEG-DOX-M inhibited cell proliferation of U87 MG cells and effectively induced cell apoptosis of U87 MG cells. Intracranial antitumor experiments showed that free DOX hardly penetrated the BBB, but CMS/PEG-DOX-M effectively reached the orthotopic ntracranial tumor through the BBB and significantly inhibited tumor growth. Immunofluorescence staining of orthotopic tumor tissue sections confirmed that nanodrugs promoted apoptosis of tumor cells. This study developed a multimodal nanodrug treatment system with the enhanced abilities of tumor-targeting, BBB penetration, and cancer-specific accumulation of chemotherapeutic drugs by combining chemotherapy and photothermal therapy. It can be used as a flexible and effective GBM treatment system and it may also be used for the treatment of other central nervous systems (CNS) tumors and extracranial tumors.

Hydrogenation of ethyl acetate to ethanol over Cu/ZnO/MOx (MOx = SiO2, Al2O3, and ZrO2) catalysts

Zhipeng Lu,Hengbo Yin,Aili Wang,Jing Hu,Wuping Xue,Haixu Yin,Shuxin Liu 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.37 No.-

The Cu/ZnO/SiO2, Cu/ZnO/Al2O3, and Cu/ZnO/ZrO2 catalysts prepared by the co-precipitation methodwere used for the catalytic hydrogenation of ethyl acetate to ethanol. The addition of ZnO in the Cu/ZnO/MOx catalysts improved their catalytic activities for the hydrogenation reaction. Small-sized coppercrystallite and high surface acidity favored the catalytic hydrogenation of ethyl acetate to ethanol. TheCu/ZnO/Al2O3 catalyst gave the ethanol selectivity of ca. 95% at the ethyl acetate conversion of ca. 80%when the reaction temperature was 280 8C. The reaction activation energy over Cu/ZnO/Al2O3 catalystwas 115 kJ mol 1, lower than those over the Cu/ZnO/SiO2 and Cu/ZnO/ZrO2 catalysts.