Delay prediction with spatial–temporal bi-directional LSTM in railway network

Yu Ke,Kong Chuiyun,Zhong Limin,Fu Junfeng,Shao Jie 한국통신학회 2023 ICT Express Vol.9 No.5

Train delay prediction is a vital part of railway system, but due to uncertain factors such as the complexity of the railway system and spatial–temporal features, it is often difficult to predict train delay in practice. In this paper, we propose a Spatial–Temporal and Bi-directional Long Short-Term Memory (ST-BiLSTM) model to deal with the train delay prediction problem. The model contains spatial–temporal blocks to capture spatial and temporal features and a bi-directional Long Short-Term Memory (LSTM) block to introduce bi-directional information through an attention mechanism. Experiments demonstrate that ST-BiLSTM outperforms the existing baselines in two evaluation metrics.

A Data-Driven Deep Learning Network for Massive MIMO Detection with High-order QAM

Yu, Yongzhi,Ying, Jie,Wang, Ping,Guo, Limin 한국통신학회 2023 Journal of communications and networks Vol.25 No.1

Massive multiple-input multiple-output (MIMO)can provide higher spectral efficiency and energy efficiencycompared to conventional MIMO systems. Unfortunately, asthe numbers of modulation orders and antennas increase, thecomputational complexity of conventional symbol detection algo-rithms becomes unaffordable and their performance deteriorates. However, deep learning (DL) techniques can provide flexibility,nonlinearity and computational parallelism for massive MIMOdetection to address these challenges. We propose an efficientdata-driven detection network, i.e., accelerated multiuser inter-ference cancellation network (AMIC-Net), for uplink massiveMIMO systems. Specifically, we first introduce an extrapolationfactor regarded as a learnable parameter into the multiuserinterference cancellation (MIC) algorithm for iterative sequentialdetection (ISD) detector through extrapolation technique toenhance the convergence performance. Then we unfold the aboveaccelerated iterative algorithm and adopt a sparsely connectedapproach, instead of fully connected, to obtain a relativelysimple deep neural network (DNN) structure to enhance thedetection performance through the data-driven DL approach. Furthermore, in order to accommodate communication scenarioswith higher-order modulation, a novel activation function isproposed, which is composed of multiple softsign activationfunctions with additional learnable parameters to implement amulti-segment mapping of the set of constellation points withdifferent modulations. Numerical results show that the proposedDL network can bring significant performance gain to ISDdetector with various massive antenna settings and outperformthe existing detectors with the same or lower computationalcomplexity, especially in high-order QAM modulation scenarios.

Hybrid-Fiber-Reinforced Composite Boards Made of Recycled Aramid Fibers: Preparation and Puncture Properties

Yu-Chun Chuang,Limin Bao,Ching-Wen Lou,Jia-Horng Lin 한국섬유공학회 2019 Fibers and polymers Vol.20 No.2

Protective textiles require massive consumption of fibers and fabrics, which is responsible for diverse highstrength fabric waste. Wrongly arranged disposal of textile waste is equivalent to the waste valuable resource while causing environmental pollutions. Aramid selvages are worthwhile recycling and used in this study. They are scattered into Aramidstaple fibers and mixed with low melting point polyester (LMPET) fibers to form the Aramid matrices employing the nonwoven process. The matrices are added to different combinations to form Aramid composite matrices and hybrid-fiberreinforced composite boards. The process of shearing, crowding, and friction helps improve the mechanical properties of the composite boards according to the evaluations of conducted tests. With the premise of minimum damage to the fibers, this study uses recycled Aramid waste to produce composite boards that have features of high performance and low productioncost. As a test result, the hybrid-fiber-reinforced composite boards with 90 wt% of recycled Aramid fibers have the optimal mechanical property and static puncture resistance.

Inhibitory Effect and Possible Mechanism of Intraurethral Stimulation on Overactive Bladder in Female Rats

Yu Tian,Limin Liao,Jean Jacques Wyndaele 대한배뇨장애요실금학회 2015 International Neurourology Journal Vol.19 No.3

Purpose: To investigate the inhibitory effect and possible mechanism of intraurethral stimulation on overactive bladder (OAB) induced by acetic acid irritation. Methods: Cystometry was performed in 13 urethane-anesthetized female rats. Intravesical infusion of 0.5% acetic acid was used to irritate the bladder and induce OAB. Multiple cystometrograms were performed with mirabegron, continuous stimulation, mirabegron plus continuous stimulation, and β3-adrenoceptor antagonist plus continuous stimulation to determine the mechanism underlying the inhibitory effect by intraurethral stimulation. Results: Infusion of acetic acid significantly decreased bladder capacity. Intraurethral stimulation at 2.5 Hz plus mirabegron significantly increased bladder capacity and decreased the nonvoiding contraction count. The changes were strongly inhibited after the β3-adrenoceptor antagonist was administered. Conclusions: Activation of urethral afferent nerves can reverse OAB, which activates C-fiber afferent nerves. This animal study indicates that intraurethral stimulation may interfere with OAB through hypogastric nerve activation and pudendal nerve neuromodulation.

Kinetics of perovskite-like oxygen carriers for chemical looping air separation

Limin Hou,Qingbo Yu,Tuo Wang,Kun Wang,Qin Qin,Zhenfei Qi 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.3

Chemical looping air separation gives an energy-efficient choice for oxygen production. We performed kinetic analysis of YBaCo4O7+δ, Y0.95Ti0.05BaCo4O7+δ, Y0.2Ti0.05Dy0.75BaCo4O7+δ, and Y0.15Zr0.1Dy0.75BaCo4O7+δ oxygen carriers in a CLAS process. TG experiments were conducted with heating rates of 0.5, 1, and 2 oC/min in a thermogravimetric analyzer. Further exploration is required to develop an appropriate oxygen carrier. So, we used the model-free approach, Starink method, to evaluate the apparent activation energy. And, masterplots method was applied to determine the most probable mechanism function. The results show that the distributed activation energies of oxidation/ reduction process are 189.42/286.22 kJ/mol, 197.70/324.87 kJ/mol, 195.41/310.4 kJ/mol, and 192.20/293.53 kJ/mol for YBaCo4O7+δ, Y0.95Ti0.05BaCo4O7+δ, Y0.2Ti0.05Dy0.75BaCo4O7+δ, and Y0.15Zr0.1Dy0.75BaCo4O7+δ oxygen carriers, respectively. Random nucleation and nuclei growth A model is the most suitable for oxidation process. The A model and D are the most suitable for the reduction process. Regarding YBaCo4O7+δ, Y0.95Ti0.05BaCo4O7+δ, Y0.2Ti0.05Dy0.75BaCo4O7+δ, and Y0.15Zr0.1Dy0.75BaCo4O7+δ kinetic, oxygen transfer materials are rate-determined by nucleation and nuclei growth. For reduction kinetic, the gas diffusion stage could also become a dominant step.

Sensitivity analysis of key factors in controlling absorption and desorption of oxygen to oxygen carriers

Limin Hou,Qingbo Yu,Kun Wang,Shuo Zhang,Qin Qin,Fan Yang 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.1

Chemical looping air separation gives an oxygen resource for the oxy-fuel combustion system. To investigate the sensitivity of operation parameters and optimal operation parameters, with the consideration of the reactor temperature, we used the oxygen concentration, and reaction gas flow, an orthogonal experiment and multi-objective comprehensive evaluation method to analyze the results obtained by fixed-bed apparatus with the YBaCo4O7+, Y0.95Ti0.05BaCo4O7+, Y0.5Dy0.5BaCo4O7+, and Y0.2Ti0.05Dy0.75BaCo4O7+ oxygen carriers. The results showed that the effects of operating conditions on oxygen absorption/desorption properties varieds in the order: oxygen concentration>gas flow rate>absorption temperature=desorption temperature. Analysis of max-min difference showed that the optimum operating conditions such as absorption temperature, 350 oC, desorption temperature, 430 oC, gas flow rate, 200 ml/min, and oxygen concentration, 21% were confirmed

Blow-up and global solutions for some parabolic systems under nonlinear boundary conditions

Limin Guo,Lishan Liu,Yonghong Wu,Yu-mei Zou 대한수학회 2019 대한수학회지 Vol.56 No.4

In this paper, blows-up and global solutions for a class of nonlinear divergence form parabolic equations with the abstract form of $(\varrho(u))_{t}$ and time dependent coefficients are considered. The conditions are established for the existence of a solution globally and also the conditions are established for the blow up of the solution at some finite time. Moreover, the lower bound and upper bound of the blow-up time are derived if blow-up occurs.

Oxygen absorption and desorption properties of YBaCo4O7+δ monolithic oxygen carrier in the fixed-bed reactor

Limin Hou,Chaoyue Qiao,Qingbo Yu,Wenfei Wu 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.3

The technology of chemical looping air separation, with the characteristics of simple operation, low cost, and low energy consumption, separates oxygen from air with the oxygen carrier. In this work, reaction properties of monolithic oxygen carriers were investigated in a fixed-bed apparatus, with the consideration of the reactor temperature, oxygen concentration, and reaction gas flow. The XRD results showed that active phase, Al2O3, and cordierite cannot react with each other in calcination processing. The SEM results showed that the micromorphology of oxygen carrier was loaded on cordierite honeycomb uniformly with sphere or sphere-like particles. Oxygen carriers show a faster oxygen release rate and a slower oxygen intake rate. With increasing of absorption temperature, oxygen concentration of inlet gas, and desorption temperature, the reaction rate per unit mass increases. With increasing of gas flow rate, the reaction rate per unit mass decreases. The maximum value of the reaction rate per unit mass was obtained by Y0.95Ti0.05BaCo4O7+δ monolith sample. Samples substituted with Dy element showed fine performance of stability, as Dy substitution causes more serious local lattice distortions.

Fuzzy Iterative Learning Control-based Design of Fault Tolerant Guaranteed Cost Controller for Nonlinear Batch Processes

Jingxian Yu,Hui Dang,Limin Wang 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.5

For nonlinear batch processes with actuator faults and external disturbances, a fault-tolerant guaranteed cost controller is proposed based on fuzzy iterative learning control. The linear process model is treated by a sector nonlinear method into a T-S fuzzy faulty model, then the obtained model is transformed into the 2D Roesser equivalent model using the two-dimensional characteristics of batch processes. Based on the obtained model and the Lyapunov stability theory, the quadratic cost function is given and the fault-tolerant guaranteed cost controller guaranteeing that the closed-loop performance index is not more than an upper bound is designed to deal with the actuator fault. The fault-tolerant controller guarantees the stable operation of the faulty system and also has the best system performance with the controller gain and the maximum performance index being solved through constrained optimization. Finally, the simulation on a strong nonlinear reactor is carried out. It shows that the proposed method is more feasible and effective than other methods.

Preparation and Electrochemical Performances of Rod-Like LiV3O8/Carbon Composites Using Polyaniline as Carbon Source

Xiao-Yu Cao,Limin Zhu,Hailian Wu 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.4

Rod-like LiV3O8/carbon composites were successfully prepared by the polymer graphitization of LiV3O8/polyaniline composites, which were synthesized through the in-situ oxidative polymerization method. The crystal phases of as-prepared samples, confirmed by X-ray diffraction, show that the interlayer spacing in LiV3O8/ carbon composites is much wider than that of the pristine LiV3O8. Compared to the bare LiV3O8, the longer and smoother rod-like LiV3O8/carbon composites, investigated by scanning electron microscope and transmission electron microscope, were covered by a continuously thin layer of fluffy carbon with a thickness of approximate 20 nm. The optimal LiV3O8/carbon composite delivered a discharge capacity of 219.37 mAh g−1 in the initial cycle, and maintained a high capacity of 263.538 mAh g−1 at the 30th cycle, which was much higher than that of the pristine LiV3O8 (227.645 mAh g−1). Cyclic voltammetry measurements disclose that, after the carbon coating treatment, the phase transition of the optimal LiV3O8/carbon composite proceeds more reversibly and smoothly during charging/discharging. The improved cyclability of the optimal LiV3O8/carbon composite should be attributed to the confinement from thin carbon layer, the structural stability, the good interfacial compatibility, and the well-preserved electrode morphology after prolonged cycles.