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140 results on '"Liu, Zhengfeng"'

1. UAV's Rotor Micro-Doppler Feature Extraction Using Integrated Sensing and Communication Signal: Algorithm Design and Testbed Evaluation

Author

Wei, Jiachen, Ma, Dingyou, He, Feiyang, Zhang, Qixun, Feng, Zhiyong, Liu, Zhengfeng, and Liang, Taohong

Subjects
Electrical Engineering and Systems Science - Signal Processing, Computer Science - Emerging Technologies
Abstract

With the rapid application of unmanned aerial vehicles (UAVs) in urban areas, the identification and tracking of hovering UAVs have become critical challenges, significantly impacting the safety of aircraft take-off and landing operations. As a promising technology for 6G mobile systems, integrated sensing and communication (ISAC) can be used to detect high-mobility UAVs with a low deployment cost. The micro-Doppler signals from UAV rotors can be leveraged to address the detection of low-mobility and hovering UAVs using ISAC signals. However, determining whether the frame structure of the ISAC system can be used to identify UAVs, and how to accurately capture the weak rotor micro-Doppler signals of UAVs in complex environments, remain two challenging problems. This paper first proposes a novel frame structure for UAV micro-Doppler extraction and the representation of UAV micro-Doppler signals within the channel state information (CSI). Furthermore, to address complex environments and the interference caused by UAV body vibrations, the rotor micro-Doppler null space pursuit (rmD-NSP) algorithm and the feature extraction algorithm synchroextracting transform (SET) are designed to effectively separate UAV's rotor micro-Doppler signals and enhance their features in the spectrogram. Finally, both simulation and hardware testbed demonstrate that the proposed rmD-NSP algorithm enables the ISAC base station (BS) to accurately and completely extract UAV's rotor micro-Doppler signals. Within a 0.1s observation period, ISAC BS successfully captures eight rotations of the DJI M300 RTK UAV's rotor in urban environments. Compared to the existing AM-FM NSP and NSP signal decomposition algorithms, the integrity of the rotor micro-Doppler features is improved by 60%.

Published
2024

8. MPC Underwater Docking Control Method Study of UUV in Complex Interference

Author

Teng, Yanbin, Liu, Changde, Liu, Zhengfeng, Zhang, Longhui, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Hirche, Sandra, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Li, Yong, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Möller, Sebastian, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Oneto, Luca, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zamboni, Walter, Series Editor, Zhang, Junjie James, Series Editor, Yan, Liang, editor, and Deng, Yimin, editor

Published
2023
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9. Research on USV Course PID Control Based on Improved Genetic Algorithm

Author

Tan, Zhikun, Wei, Naxin, Liu, Zhengfeng, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Hirche, Sandra, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Li, Yong, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Möller, Sebastian, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Oneto, Luca, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zamboni, Walter, Series Editor, Zhang, Junjie James, Series Editor, Yan, Liang, editor, and Deng, Yimin, editor

Published
2023
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13. Flood Forecasting through Spatiotemporal Rainfall in Hilly Watersheds.

Author

Liu, Yuanyuan, Liu, Yesen, Liu, Yang, Liu, Zhengfeng, Yang, Weitao, and Li, Kuang

Subjects
FLOOD forecasting, RAINFALL, ARTIFICIAL intelligence, LEAD time (Supply chain management), FLOOD risk
Abstract

Flood prediction in hilly regions, characterized by rapid flow rates and high destructive potential, remains a significant challenge. This study addresses this problem by introducing a novel machine learning-based approach to enhance flood forecast accuracy and lead time in small watersheds within hilly terrain. The study area encompasses small watersheds of approximately 600 km2. The proposed method analyzes spatiotemporal characteristics in rainfall dynamics to identify historical rainfall–flood events that closely resemble current patterns, effectively "learning from the past to predict the present". The approach demonstrates notable precision, with an average error of 8.33% for peak flow prediction, 14.27% for total volume prediction, and a lead time error of just 1 h for peak occurrence. These results meet the stringent accuracy requirements for flood forecasting, offering a targeted and effective solution for flood forecasting in challenging hilly terrains. This innovative methodology deviates from conventional techniques by adopting a holistic view of rainfall trends, representing a significant advancement in addressing the complexities of flood prediction in these regions. [ABSTRACT FROM AUTHOR]

Published
2024
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22. Orthogonal optimization design of a Sirocco fan and numerical analysis on the internal flow characteristics.

Author

Liu, Zhengfeng, Wang, Zhengdao, Du, Shouhua, Yang, Hui, Wei, Yikun, and Zhang, Wei

Subjects
FLOW separation, NUMERICAL analysis, STATIC pressure, FLOW instability, IMPELLERS
Abstract

The forward-curved multi-blade centrifugal fan, also termed as Sirocco fan, is characterized by its complex characteristics of internal flow within the impeller and volute. Currently most of the fans are designed with modifications or optimizations for certain geometric parameters which could not ensure the well compatibility of flow in the impeller and volute, thus it is difficult to improve the aerodynamic performances of the fans. In this paper, we performed a multi-parameter design of a Sirocco fan with optimizations on the geometric parameters of the impeller and volute. The geometric parameters of the volute were designed based on analysis of the internal flow patterns, and the influence from the impeller is also considered. Optimization on the geometric parameters was carried out using the steepest descent method to improve the static pressure rise and efficiency under the designed flow rate by taking into account the relevance of flow in the impeller and volute. The effect of the parametric optimization is evaluated and analyzed by large-eddy simulation (LES). It was found that the static pressure rise and efficiency of the optimized model increase by 1.8% and 5.0% compared with the baseline model, respectively. The static pressure rise fluctuates in a regularly periodic manner. The optimized model reduces the area of low-pressure recirculating flow at the center of the fan and the separated flow on the suction surface of the blades. The near-wall flow on the volute surface is more stable, and the pressure fluctuation around the volute tongue is reduced. The outflow of the volute exhibits better uniformity than the baseline model. [ABSTRACT FROM AUTHOR]

Published
2024
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36. Clinical features and 18F-FDG PET/CT for distinguishing of malignant lymphoma from inflammatory lymphadenopathy in HIV-infected patients.

Author

Chen, Donghe, Zhu, Yunqi, Chen, Yunbo, Zhu, Danhua, Liu, Zhengfeng, Li, Tiancheng, Liu, Yinuo, Zhao, Kui, Su, Xinhui, and Li, Lanjuan

Abstract

Background: It is vital to distinguish between inflammatory and malignant lymphadenopathy in human immunodeficiency virus (HIV) infected individuals. The purpose of our study was to differentiate the variations in the clinical characteristics of HIV patients, and apply 18F-FDG PET/CT parameters for distinguishing of malignant lymphoma and inflammatory lymphadenopathy in such patients.Methods: This retrospective cross-sectional study included 59 consecutive HIV-infected patients who underwent whole-body 18F-FDG PET/CT. Of these patients, 37 had biopsy-proven HIV-associated lymphoma, and 22 with HIV-associated inflammatory lymphadenopathy were used as controls. The determined parameters were the maximum of standard uptake value (SUVmax), SUVmax of only lymph nodes (SUVLN), the most FDG-avid lesion-to-liver SUVmax ratio (SURmax), laboratory examinations and demographics. The optimal cut-off of 18F-FDG PET/CT value was analyzed by receiver operating characteristic curve (ROC).Results: Considering the clinical records, the Karnofsky Performance Status (KPS) scores in patients with inflammatory lymphadenopathy were obviously higher than those in patients with malignant lymphoma (P = 0.015), whereas lymphocyte counts and lactate dehydrogenase (LDH) were obviously lower (P = 0.014 and 0.010, respectively). For the 18F-FDG PET/CT imaging, extra-lymphatic lesions, especially digestive tract and Waldeyer's ring, occurred more frequently in malignant lymphoma than inflammatory lymphadenopathy. Furthermore, the SURmax and SUVLN in malignant lymphoma were markedly higher than those in inflammatory lymphadenopathy (P = 0.000 and 0.000, respectively). The cut-off point of 3.1 for SURmax had higher specificity (91.9%) and relatively reasonable sensitivity (68.2%) and the cut-off point of 8.0 for the SUVLN had high specificity (89.2%) and relatively reasonable sensitivity (63.6%).Conclusion: Our study identified the distinctive characteristics of the clinical manifestations, the SURmax, SUVLN and detectability of extra-lymphatic lesions on 18F-FDG PET, and thus provides a new basis for distinguishing of malignant lymphoma from inflammatory lymphadenopathy in HIV-infected patients. [ABSTRACT FROM AUTHOR]

Published
2022
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37. Flow instability in a volute-free centrifugal fan subjected to non-axisymmetric pre-swirl flow from upstream bended inflow tube.

Author

Liu, Zhengfeng, Yang, Hui, He, Haijiang, Yu, Peiquan, Wei, Yikun, and Zhang, Wei

Subjects
FLOW instability, STATIC pressure, SWIRLING flow, TUBES
Abstract

The characteristics of internal flow and performance of a centrifugal fan is greatly dependent on the inflow pattern. As the fan is subjected to incoming flow from an upstream tube, the size and geometry of the tube affect the three-dimensional motion of local flow and possibly degrades the aerodynamic performance of the fan. In this work, we performed a numerical investigation on the internal flow in a centrifugal fan subjected to incoming flow from an upstream bended inflow tube of various radii using the steady and unsteady Reynolds-averaged Navier-Stokes (RANS and URANS) simulation approaches. The effects of the non-axisymmetric pre-swirl flow generated due to the curvature of the bended inflow tube are demonstrated by analyzing the internal flow characteristics of the fan, including the spatial distributions and temporal variations of pressure field and streamlines, pressure fluctuations in the upstream tube, the inflow and outflow sections of the impeller, and the circumferential distributions of velocity and pressure in the impeller. The numerical results reveal that as the inflow tube is curved with larger curvature (smaller radius of the bended section), the pre-swirl inflow is strong and deteriorates the static pressure rise and static pressure efficiency of the centrifugal fan more remarkably, and the circumferential non-uniformity of pressure and velocity distributions appears inside of the channels of the fan. As the radius of the bended section increases, the instability of the internal flow gets more pronounced, as represented by the stronger pressure fluctuations at the inflow and outflow sections. The prediction capabilities of RANS and URANS approaches are also analyzed based on the numerical data and we found that the latter is more reliable in predicting the performance of the fan. [ABSTRACT FROM AUTHOR]

Published
2022
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38. The Mechanical Behavior of Predrilled-Hole Concrete Micro-Pile in Integral Abutment Jointless Bridges (IAJBs)

Author

Shan Yulin, Zhou Zhiming, Liu Zhengfeng, He Lingfeng, and Huang Fuyun

Subjects
General Relativity and Quantum Cosmology, Materials science, Astrophysics::High Energy Astrophysical Phenomena, Bending moment, medicine, Stiffness, Displacement (orthopedic surgery), Integral abutment, Bearing capacity, Composite material, medicine.symptom, Pile
Abstract

In order to investigate the effects of different predrilled-hole parameters on the mechanical behavior of micro-piles, Pseudo-static tests on five predrilled-hole micro-piles were carried out under unidirectional cyclic displacement load. The displacement-load curves and distribution of bending moment and displacement are analyzed. The test results indicated that the smaller the stiffness of predrilled-hole filler is, the better the deformability of specimen is. The stiffness of predrilled-hole filler has significant influence on the displacement and bending moment of pile body. Compared with the shallow predrilled-hole specimen, the deep predrilled-hole specimen has lower bearing capacity, but its deformability and bending moment are larger. The larger the diameter of predrilled-hole is, the larger the bending moment of specimen is. The larger diameter of predrilled-hole has significant effect on displacement of specimen. The deformability of predrilled-hole specimen is improved when the depth and diameter of predrilled-hole exceed 3 times of pile diameter.

Published
2020

46. On-line monitoring of ash fouling and soot-blowing optimization for convective heat exchanger in coal-fired power plant boiler

Author

Yuanhao Shi, Liu Zhengfeng, and Jingcheng Wang

Subjects
Engineering, Thermal efficiency, Waste management, Fouling, Power station, Convective heat transfer, business.industry, Boiler (power generation), Energy balance, Energy Engineering and Power Technology, Industrial and Manufacturing Engineering, Energy conservation, Heat transfer, Process engineering, business
Abstract

This paper presented a comprehensive approach of on-line monitoring and optimization for the soot-blowing system in coal-fired power plant boilers. Due to ash fouling monitoring of heat transfer surfaces of the boiler based on dynamic mass and energy balance method, on-line calculation of boiler thermal efficiency and soft measurements for gas flow rate at the double breezing tail and steam flow rate of reheaters, the performance of boiler's soot-blowing system can be evaluated on-line. And then, the suitable soot-blowing strategies are developed for soot-blowing frequencies and duration optimization. Monitoring results and analysis of an experimental application are given to illustrate the proposed methodologies. The methods proposed in this paper can be applied to state assessment and guidance of soot-blowing operation of boiler's soot-blowing system in order to achieve the purpose of energy conservation, without demanding special instruments or complex computing systems.

Published
2015

47. The proliferation of malignant melanoma cells could be inhibited by ranibizumab via antagonizing VEGF through VEGFR1

Author

Li, Jiao, Cui, Yan, Wang, Qin, Guo, Dadong, Pan, Xuemei, Wang, Xingrong, Bi, Hongsheng, Chen, Wei, Liu, Zhengfeng, and Zhao, Shengya

Subjects
Adult, Uveal Neoplasms, Vascular Endothelial Growth Factor A, Vascular Endothelial Growth Factor Receptor-1, genetic structures, Cell Death, Ciliary Body, Retinal Pigment Epithelium, Antibodies, Monoclonal, Humanized, Immunohistochemistry, Cell Line, Computer Systems, Ranibizumab, Humans, Melanoma, Research Article, Cell Proliferation
Abstract

Purpose Angiogenesis is an important mediator in tumor progression. Vascular endothelial growth factor (VEGF) is one of the major cytokines that can influence angiogenesis. However, the potential mechanism of tumor growth inhibition through anti-VEGF agents is still unclear. This study was performed to examine whether ranibizumab could inhibit malignant melanoma growth in vitro and to determine the safety of ranibizumab on human adult retinal pigment epithelium cell line (ARPE-19 cells). Methods Malignant melanoma cells obtained from a clinic were cultured in vitro. VEGF concentrations secreted by malignant melanoma cells and the ARPE-19 cells were examined by enzyme-linked immunosorbent assay (ELISA). The two kinds of cells were both treated with VEGF and its antagonist, ranibizumab. The dynamic changes of the two types of cells were monitored by real-time cell electronic sensing (RT-CES) assay. The effect of ranibizumab on both types of cells was verified by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl (MTT) assay. The expression of VEGF receptor 1 (VEGFR1) RNA in uveal melanoma was further investigated through the PCR technique. Results The levels of VEGF secreted by malignant melanoma cells were much higher than those of ARPE-19 cells, and were markedly decreased in the action of 0.1 mg/ml ranibizumab. However, there was no obvious reduction of VEGF in the presence of ranibizumab for ARPE-19 (p>0.05). Meanwhile, RT-CES showed that the viability of malignant melanoma cells increased greatly in the presence of VEGF. When VEGF was 20 ng/ml, viability of the malignant melanoma cells increased by 40% compared with the negative control. There was no evident effect on proliferation of ARPE-19 (p>0.05). Furthermore, the growth of malignant melanoma cells was obviously inhibited after ranibizumab intervention. When ranibizumab was administered at 0.25 mg/ml, the survival rate of the malignant melanoma cells decreased to 57.5%. Nevertheless, low-dose exposure to ranibizumab had only a slight effect on the growth of ARPE-19, and PCR result demonstrated that VEGFR1 plays a role in this tumor tissue rather than VEGFR2. Conclusions Ranibizumab can selectively inhibit malignant melanoma cell proliferation by decreasing the expression of VEGF; the possible mechanism of the inhibitory effect may involve VEGFR1 antagonism.

Published
2014

50. Clustering LS-SVM models for the prediction of unburned carbon content in fly ash

Author

Jingcheng Wang, Weijing Shi, Liu Zhengfeng, and Yuanhao Shi

Subjects
Engineering, Basis (linear algebra), business.industry, chemistry.chemical_element, computer.software_genre, Fuzzy logic, Support vector machine, ComputingMethodologies_PATTERNRECOGNITION, chemistry, Fly ash, Content (measure theory), Least squares support vector machine, Data mining, business, Cluster analysis, Carbon, computer
Abstract

This paper investigates factors that influences the unburned carbon content in fly ash and selects the optical factors from the original characteristics by means of minimal-redundancy-maximal-relevance criterion (mRMR). And on this basis, this paper proposes a novel model called clustering least squares support vector machine (CLS-SVM) to predict the unburned carbon content in fly ash. In this CLS-SVM model, a fuzzy c-means cluster algorithm (FCM) is adopted to decompose the original data into three different sub data sets. Taking advantage of both theory of clustering algorithm and advanced statistical learning methodology, CLS-SVM models are built specifically for each different sub data sets. Then the CLS-SVM models are developed to predict the key parameter — unburned carbon content, which is verified through operation data of a 300MW generating unit.

Published
2015

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