Uplink Achievable Rate analysis of Massive MIMO Systems in Transmit-correlated Ricean Fading Environments

Yixin Xu,Fulai Liu,Zixuan Zhang,Zhenxing Sun 한국인터넷정보학회 2023 KSII Transactions on Internet and Information Syst Vol.17 No.1

In this article, the uplink achievable rate is investigated for massive multiple-input multiple-output (MIMO) under correlated Ricean fading channel, where each base station (BS) and user are both deployed multiple antennas. Considering the availability of prior knowledge at BS, two different channel estimation approaches are adopted with and without prior knowledge. Based on these channel estimations, a two-layer decoding scheme is adopted with maximum ratio precoding as the first layer decoder and optimal second layer precoding in the second layer. Based on two aforementioned channel estimations and two-layer decoding scheme, the exact closed form expressions for uplink achievable rates are computed with and without prior knowledge, respectively. These derived expressions enable us to analyze the impacts of line-of-sight (LoS) component, two-layer decoding, data transmit power, pilot contamination, and spatially correlated Ricean fading. Then, numerical results illustrate that the system with spatially correlated Ricean fading channel is superior in terms of uplink achievable rate. Besides, it reveals that compared with the single-layer decoding, the two-layer decoding scheme can significantly improve the uplink achievable rate performance.

Stress Localization in Brittle Rock-Like Samples of Particle-Filled Joints under Direct Shear Loading

Gang Wang,Yixin Liu,Jiang Xu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.1

The mechanical strength and stability of particulate materials are controlled by their frictional behavior, which plays a vital role in evolving of landslides and geological hazards. While deformation of particles is closely related to the stress localization, the shear displacement processes controlling local stresses are difficult to be observed directly. In this paper, the laboratory direct shear experiments were designed to explore the relationship between local stresses and particles’ behavior, as well as clarify the particle size effect on the particle-filled joint’s mechanical properties. A new method was proposed, which combined the 3D scanning technology and statistical analysis for reconstructing the aperture distribution evolution during the shear process. The local stress regions were assessed by analyzing the aperture evolution. The direct shear tests on artificial joints filled with particles of different sizes were conducted with a normal load of 30 kN. The results obtained proved that the filled joint's mechanical behavior had a close correlation with the particle size, which involved not only the peak strength but also the residual shear strength. The particles’ deformation determined the normal strain, while the shear displacement controlled the aperture distribution, further influencing the local stress. Three modes of particle deformation were proposed based on the analysis of mechanical behavior and the local stress region. The findings of this study are considered instrumental in investigating failure mechanism with an increasing fault or landslide displacement that may trigger localization–delocalization events and, therefore, control the macroscopic stability and prevent the occurrence of potential geological hazards.

Study on the Micro-vibration Suppression of a MnCu Spring Isolation Platform with Low Stiffness and High Damping

Xianbo Yin,Yang Xu,Xiaowei Sheng,Song Wan,Yixin Wang 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.3

Reaction wheels are the primary micro-vibration sources for microsatellites. To reduce the adverse effects of micro-vibrations, a six-degree-of-freedom (6-DOF) vibration isolation scheme with low stiffness and high damping is proposed. Through six-component force measurements, the harmonic characteristics of the micro-vibrations generated by a reaction wheel are determined. Based on an assumption of small deformation linear elasticity, a dynamic model of a convergent isolation platform is established. With high damping characteristics, helical springs made of MnCu (manganese copper) alloy are selected as the isolation element of the platform. After a modal analysis and stiffness design, the key structural parameters of the isolator are determined. According to the coupling of degrees of freedom, the transmissibility of the isolator is simulated and compared to titanium and aluminum alloys. Combined with on-ground and on-board tests, the effectiveness of the isolation platform is verified. The research shows that the 6-DOF isolation platform based on the MnCu spring realizes multidirectional low-frequency and low-magnitude micro-vibration suppression. The minimum initial isolation frequency of the designed isolator is 16.8 Hz, and the best suppression effect reaches 17.5 dB. The proposed isolator’s application successfully controls high-order harmonics and sensitive load response behaviors.

Identification of a novel prognostic signature composed of 3 cuproptosis-related transcription factors in colon adenocarcinoma

Zhou Lei,Zhang Yuwan,Xu Yixin,Jiang Tao,Tang Liming 한국유전학회 2023 Genes & Genomics Vol.45 No.8

Background Since the mechanism of cuproptosis was recently revealed, many molecules related to this pathway have been widely concerned and exploited to have prognostic potential. However, it is still unknown whether the transcription factors related to cuproptosis could be competent as tumor biomarkers of colon adenocarcinoma (COAD). Objective To analyze the prognostic potential of cuproptosis-related transcription factors in COAD, and validate the representative molecule. Methods Transcriptome data and patients’ clinical parameters were obtained from the TCGA and GEO database. 19 cuproptosis genes were identified through literature consulting. Cuproptosis-related transcription factors were screened by COX regression analyses. Multivariate Cox regression was applied to construct the signature. Prognostic effects were evaluated by Kaplan Meier survival analyses and ROC analyses. KEGG, GO, and ssGSEA analyses were performed for function prediction. 48 COAD tissues were collected for immunohistochemistry stain to observe the expression level and prognostic value of E2F3. qRT-PCR was performed to detect mRNA expression levels, while cell viability assay was applied to detect the response of COAD cells to elesclomol treatment. Results A novel signature based on 3 prognostic transcription factors related to cuproptosis was successfully established and verified. Patients in the low-risk group tended to have better overall survival and lower immune phenotype scores than those in the high-risk group. Meanwhile, we also constructed a nomogram based on this signature and predict 10 candidate compounds targeting this signature. As an essential member of this signature, E2F3 was confirmed to be overexpressed in COAD tissues and was associated with poor prognosis of COAD patients. Importantly, CuCl2 and cuproptosis inducer elesclomol treatment could increase the expression of E2F3 in COAD cell while the overexpression of E2F3 significantly enhanced the resistance of COAD cells to elesclomol treatment. Conclusion Our research has identified a new prognostic biomarker and provides some innovative insights into the diagnosis and therapy of patients with COAD.

Design and Implementation of a Universal System Control Strategy Applicable to VSC-HVDC Systems

Yue Zhao,Libao Shi,Yixin Ni,Zheng Xu,Liang-Zhong Yao 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

This paper proposes a universal system control strategy for voltage source converter (VSC) based high voltage direct current (HVDC) systems. The framework of the designed control strategy consists of five layer structures considering the topology and control characteristics of the VSC-HVDC system. The control commands sent from the topmost layer can be transmitted to the next layer based on the existing communication system. When the commands are sent to each substation, the following transmission of commands between the four lower layers are realized using the internal communication system while ignoring the communication delay. This hierarchical control strategy can be easily applied to any VSC-HVDC system with any topology. Furthermore, an integrated controller for each converter is designed and implemented considering all of the possible operating states. The modular-designed integrated controller makes it quite easy to extend its operating states if necessary, and it is available for any kind of VSC. A detailed model of a VSC-HVDC system containing a DC hub is built in the PSCAD/EMTDC environment. Simulation results based on three operating conditions (the start-up process, the voltage margin control method and the master-slave control method) demonstrate the flexibility and validity of the proposed control strategy.

Fast Supplementary Voltage Control Strategy to Mitigate Catastrophic Trip-off Risk of Wind Turbines

Yin Lifu,Liu Yongcheng,Wang Zhuxiu,Xu Ang,Li Zhengtian,Lin Xiangning,Feng Zhongnan,Zhuo Yixin 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.6

There exists such a risk that Magnetic Control Reactor (MCR) type Static Var Compensator (SVC), which is widely used in wind farms, still outputs excessive reactive power after fault removal in the wind farm due to the slow regulating speed of MCR, leading to catastrophic trip-off problem of wind turbine. For the purpose of overcoming the shortage of MCR-type SVC on regulating speed and eff ectively controlling the transient over-voltage level of wind farm due to fault removal, an novel fast supplementary voltage control strategy for MCR-type SVC based on decision tree algorithm is proposed. The over-voltage level and trip-off risk of each wind turbine after fault removal is predicted by the proposed dynamic voltage security decision tree system. According to the predictions, appropriate capacitor banks are shed to lower the risk of wind turbine trip-off due to overvoltage, resulting from reactive power over-compensation. It can be proven with case studies that the proposed strategy is capable of reducing the risk of over-voltage in wind farms, accompanied by the excellent computational effi ciency.

The construction of the Ni/La2O2CO3 nanorods catalysts with enhanced low-temperature CO2 methanation activities

Hui Yang,Xueying Wen,Siyuan Yin,Yixin Zhang,Cai-e Wu,Liang Xu,Jian Qiu,Xun Hu,Leilei Xu,Mindong Chen 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.128 No.-

In this work, the La(OH)3 nanorods were successfully synthesized by precisely regulating the parametersof the hydrothermal method. Then, a series of Ni-based CO2 methanation catalysts were fabricated via theincipient-wetness impregnation and deposition–precipitation methods by employing the La(OH)3 nanorodsas the supports. The influences of the support morphology and the preparation method on the metalsupportinteraction, Ni dispersion, and the surface basicity were carefully investigated based on varioustechniques, such as XRD, SEM, H2-TPR, CO2-TPD, XPS, ect. It was found that the rod-shaped La(OH)3 supportedcatalyst prepared by the deposition–precipitation method performed the optimum activity andstability. The reason for this could be derived from the confinement effect of the crystal plane of therod-shaped support, which would promote the formation of the strong metal-support interaction andthe construction of the Ni-La interface with high activity. Furthermore, the online-tandem TG-MS andin-situ DRIFTS technologies were used to investigate the thermal decomposition performance of the catalystprecursors in the calcination process and the reaction intermediates of the CO2 methanation. Therefore, the fundamental roles of support morphology and catalyst preparation method were expectedto direct the advancement of the Ni-based nanostructured catalysts with outstanding low-temperatureperformances.

Experimental study and analysis on physicochemical properties of coal treated with clean fracturing fluid for coal seam water injection

Gang Zhou,Cunmin Wang,Qi Wang,Yixin Xu,Zhanyi Xing,Baoyong Zhang,Cuicui Xu 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.108 No.-

In the process of coal seam water injection, the components of different fracturing fluids have differenteffects on coal. To analyze the effect of water injection fracturing fluid on the physical and chemical propertiesof coal, we studied the relationship between guar-based fracturing fluid and cationic clean fracturingfluid (C-VES). Microscopic experiments show that guar-based fracturing fluid has a certain viscosityeffect on coal, while C-VES can adsorb and capture the primary coal dust in coal. FTIR analysis shows thatC-VES has a great change on the content of coal functional groups, and guar-based fracturing fluid haslittle effect on coal. Industrial analysis shows that C-VES can better reduce the ash content of coal andhas a certain impact on the thermal efficiency of coal than guar based fracturing fluid. Combustion characteristicexperiment shows that guar-based fracturing fluid does not affect the combustion effect of coal,and C-VES can expand the exothermic temperature range of coal but has little effect on the main combustionof coal. Molecular dynamics simulation results show that C-VES has the best wetting effect oncoal. This research provides theoretical guidance for dust prevention and improving the use and conversionefficiency of coal.