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28 June 2024, Volume 50 Issue 3 Previous Issue    Next Issue

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Materials Science and Engineering

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Molecular dynamics simulation of the deposition process of cold sprayed Fe0.5CrMnAlCu mixed metal coating WEN Jie, WANG Zhao-qin, MA Deng-pan, YUAN Yu-dong, FENG Li 2024, 50 (3):  1-8.  Abstract ( 101 )   PDF (7406KB) ( 87 )   Save The molecular dynamics method was used to simulate the minimum deposition temperature of different metal powders in the process of low pressure cold spraying. The calculation results showed that Mn particles can be effectively deposited at 600 K, Fe particles need a spraying temperature of 700 K and above, and Cr particles need 1 100 K and above to be deposited effectively. Al and Cu particles can be effectively deposited in the temperature range of 500~800 K, and the maximum flattening rate of the two particles exceeds 0.6. When the powders of different metal elements are mixed and deposited at 700 K, due to the interaction and tamping effect of different powder particles during the deposition process, even if the Cr particles do not reach the deposition conditions, the Cr particles are also deposited in the coating like other element particles. References | Related Articles | Metrics

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Research on high temperature rheological behavior and hot processing map of 15CrMo alloy steel ZHOU Gao-xiong,LIANG Zheng-long, CHEN Wei-jun NIU Li-qun, WANG Xu-ming 2024, 50 (3):  9-13.  Abstract ( 55 )   PDF (3278KB) ( 28 )   Save The thermal deformation behavior of 15CrMo alloy steel was investigated through isothermal hot compression tests conducted at temperatures ranging from 900 ℃ to 1 100 ℃, and strain rates ranging from 0.01 s－1 to 1 s－1 were examined. The true stress-strain curves of the alloy under high-temperature conditions were obtained, and a modified Hansel-Spittel constitutive model adapted for the rheological behavior of 15CrMo alloy was developed. The relative error of the modified model was only 2.82%. Based on the modified constitutive model, hot processing maps are constructed for strains ranging from 0.1 to0.6. According to these maps, the optimal hot processing temperature range for 15CrMo alloy steel is 900 ℃ to 1 025 ℃, with an optimal strain rate range of 0.01 s－1 to 0.055 s－1. References | Related Articles | Metrics

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Preparation and tribological properties of Ni60 composite coating modified with glass powder WEN Hong-wu, YU Lun, ZHANG Peng, CHEN Shao-juan LI Fu-shun, HAN Yan-bing 2024, 50 (3):  14-20.  Abstract ( 59 )   PDF (7377KB) ( 29 )   Save The nickel-based alloy/glass powder composite coating was prepared on the surface of 45 steel by flame spraying technology. The coating was analyzed by scanning electron microscopy (SEM), energy spectrum analysis (EDS), X-ray diffraction analysis (XRD), microhardness analysis and pin-disk friction wear test. The effects of the amount of glass powder on the microstructure, phase composition, hardness and tribological properties of the nickel-based coating were studied. The results showed that the microhardness of the composite coating increases first and then decreases with the increase of glass powder content, and the maximum hardness reach 681 HV0.2. The friction coefficient and volume wear rate of the composite coating decrease first and then increase. The friction coefficient of the composite coating with 10% glass powder addition is as low as 0.13, and the wear rate is as low as 0.21×10－5 mm3/(N·m),which show that the addition of appropriate glass powder is beneficial to the improvement of the tribological properties of thenickel-based alloy coating. References | Related Articles | Metrics

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Highly efficient non-doped blue organic electroluminescent devices based on BCzVB ZOU Wen-jing, WU You-zhi, ZHANG Cai-rong 2024, 50 (3):  21-26.  Abstract ( 47 )   PDF (2059KB) ( 40 )   Save Efficient non-doped blue organic light-emitting device with a structure of ITO/MoO3/TAPC (1,1-bis((di-4-tolylamino)phenyl)cyclohexane,50 nm)/BCzVB (1,4-bis[2-(3-N-ethylcarbazoryl) vinyl]benzene,x nm)/CBP (4,4’-N,N’-dicarbazole-biphyenyl,20 nm)/BCzVB (x nm)/TPBi (1,3,5-tris(1-phenyl-1H-benzimidazol -2-yl)benzene,20 nm)/LiF (1.5 nm)/Al were reported, in which two ultrathin layers of BCzVB as blue emitters were located at both the sides of ambipolar material CBP. When the thickness of BCzVB is 0.3 nm, the maximum luminance and external quantum efficiencyare 12 800 cd/cm2 and 2.1% (current efficiency is 2.8 cd/A),respectively, and CIE-1931 coordinate is (0.15,0.17). The device performance is further improved by optimizing the thickness of the hole injection layer MoO3. The maximum luminance and external quantum efficiency reach 14 200 cd/cm2 and 4.2% (5.66 cd/A),respectively, which is so far the highest efficiency for BCzVB based blue OLED reported in the literature. References | Related Articles | Metrics

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Study on preparation and polishing performance of rare earth polishing powder by precipitation from (LaCe)2(SO4)3 with Mg(HCO3)2 ZHANG Quan-xin, LI Hu-ping, SHI Jun-long, SU Ai, JIN Yu-pei, XIE Hao 2024, 50 (3):  27-32.  Abstract ( 49 )   PDF (3077KB) ( 24 )   Save The initial feed liquid was lanthanum cerium sulfate solution produced from Baotou mixed rare earth ore after intensive roasting with concentrated sulfuric acid, water leaching, neutralization and impurity removal, and P507 transformation before pre-classification. The precipitant was magnesium bicarbonate solution, which was prepared by alkali conversion and carbonization of the magnesium sulfate wastewater. La&Ce rare earth polishing powder was successfully prepared by precipitation, fluorination, roasting, crushing, and grading. The morphology, phase, and polishing performance of La&Ce polishing powder were characterized. The results showed that La&Ce rare earth polishing powder particles are well-formed and evenly distributed. The K9 glass was used for performance testing of prepared polishing powder. The polishing results showed that the accumulated polishing rate reaches 352 mg after 120 minutes, and the surface roughness Sa reduce from the initial 2.0 nm to 1.742 nm. In contrast, lanthanum-cerium polishing powder prepared by precipitation of (LaCe)Cl3 with NH4HCO3 achieves a lower polishing rate of only 299 mg under the same polishing conditions,and the surface roughness Sa decrease to 1.767 nm from the initial 2.0 nm. As a consequence, the comprehensive performance of rare earth polishing powder prepared by Mg(HCO3)2 precipitation (LaCe)2(SO4)3 process is superior while maintaining the same polishing quality. References | Related Articles | Metrics

Mechanical Engineering and Power Engineering

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The influence of obstacles on the cavitation flow field in the axial-flow pump ZHAO Wei-guo, ZHANG Cui-lian, ZAKIR Khan, KOU Xiang-ru ZHOU Zhong-liang, LUO Yun-xia 2024, 50 (3):  33-41.  Abstract ( 51 )   PDF (6736KB) ( 52 )   Save Cavitation will affect the normal and stable operation of the pump. In order to explore a strategy that can effectively inhibit the development of cavitation in an axial flow pump, a method of arranging rectangular flow obstacles on the back of the axial flow pump vanes is proposed. Taking an axial-flow pump with a specific revolution of 700 as the research object, the influence of obstacles on the external characteristics and cavitation performance of the axial-flow pump was analyzed by using the full-channel unsteady numerical simulation. The results show that, under design conditions, the improved model with obstacle arrangement consistently reduces the cavity volume across all stages, especially when the cavity develops to the position of the obstacle, achieving a reduction in the cavity volume by 72.5%. The arrangement of obstacles increases the pressure at the back outlet of the blade, restricts the expansion of the low-pressure area to the outlet, reduces the adverse pressure gradient, blocks the deflection at the hub side, clears the flow line of cavitation development, optimizes the flow field structure, and inhibits the development of cavitation, consequently increasing the fracture head by 10.19%. References | Related Articles | Metrics

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Method of predicting remaining useful life of rolling bearing combining GCN and LSTM DU Xian-jun, LIU Cong 2024, 50 (3):  42-50.  Abstract ( 60 )   PDF (6079KB) ( 55 )   Save Aiming at the problem that the prediction of remaining useful life (RUL) of rolling bearings lacks reliable indicators to describe their health status due to the nonlinearity and non-stationarity of vibration signals, a prediction method combining graph convolutional network (GCN) and long short-term memory (LSTM) networks is proposed in this paper. Firstly, the bearing vibration signal is decomposed by empirical mode decomposition (EMD) to obtain the intrinsic mode functions (IMF), followed by normalization of the IMFs, and computation of adjacency and characteristic matrix; Secondly, the adjacency and feature matrix are used as the inputs of GCN to capture the data relationship and mine the deep features. Then, these deep features, along with the IMFs, are input into the LSTM network to realize time series relationship modeling and construct health indicators (HI). Finally, after using the moving average filter to eliminate the oscillation, the HI was polynomial fitted to calculate the threshold moment and determine the bearing RUL. Taking the IEEE PHM 2012 data challenge data set and XJTU-SY rolling bearing accelerated test data set as objects, the proposed method is verified. The experimental results show that when using HI constructed by GCN-LSTM model for rolling bearing RUL prediction, the prediction results closely approximate the real value, which has certain advantages in practical application. References | Related Articles | Metrics

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Research on fault diagnosis of rolling bearing based on ICEEMDAN and Hilbert envelope spectrum ZHANG Bin, CHENG Hang, MENG Qian 2024, 50 (3):  51-57.  Abstract ( 61 )   PDF (1182KB) ( 22 )   Save In addressing the challenge of extracting fault characteristic frequencies from non-stationary vibration signals in rolling bearings, a fault diagnosis method of rolling bearing was proposed based on Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (ICEEMDAN) and Hilbert envelope spectrum method. First of all, the ICEEMDAN was used to decompose the fault signals into a series of Intrinsic Mode Function (IMF). Subsequently, the valid IMFs with high correlation to the original signal were extracted, and their corresponding Hilbert envelope spectrum was generated to extract the fault characteristics frequency of the rolling bearing. Through signal analysis of the outer and inner ring faults of rolling bearings and comparison with Empirical Mode Decomposition (EMD), it is demonstrated that the amplitude of the envelope spectrum after the decomposition based on the ICEEMDAN method can clearly reflect the characteristic frequency of bearing faults. The results affirm the effectiveness of this method in diagnosing the outer and inner ring faults of rolling bearings. References | Related Articles | Metrics

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Aerodynamic performance analysis of new horizontal-axis spiral wind turbines SONG Ke, KANG Yu-chi 2024, 50 (3):  58-63.  Abstract ( 61 )   PDF (2551KB) ( 36 )   Save In order to expand the application scope of horizontal-axis wind turbines, the aerodynamic performance of the two new horizontal-axis spiral wind turbines and their ducted types are investigated by three-dimensional computational fluid dynamics simulation. The results show that the variable-angle spiral wind turbine has a higher power coefficient (CP) than the constant-angle spiral wind turbine in the lower tip-speed ratio (TSR) range. Moreover, the variable-angle spiral wind turbine has a lower thrust coefficient (CT) across the whole TSR range compared to the constant-angle spiral wind turbine, with the difference in CT between the two spiral wind turbines increases as TSR grows. The high-pressure areas of the two spiral wind turbines mainly concentrate at the front of the hub, the windward side of first-order, and second-order rotating blades.Conversely, the low-pressure areas mainly gather at the leeward side of third-order rotating blades and the hub’s rear end. The wake recovery of the variable angle spiral wind turbine is faster than that of the fixed angle spiral wind turbine due to the blockage degree of the front rotating blade is relatively small. In addition, the duct can significantly improve CP and CT of the two spiral wind turbines, widening the TSR range of CP. The results reveal the aerodynamic performance of horizontal-axis spiral wind turbines, providing valuable references for the optimizing the design and promoting the application of this type of wind turbines. References | Related Articles | Metrics

Chemical Industry and Light Industry

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Mechanical response of buried pipeline in non-uniform settlement area LU Guo-hong, XIE Rui, GUO Jian-ming, LUO Fei, LIU Xiao-bo, ZHANG Jie 2024, 50 (3):  64-68.  Abstract ( 52 )   PDF (4633KB) ( 31 )   Save The non-uniform settlement of the stratum is one of the common geological disasters faced by buried pipes, which affects the safe operation of pipes. The pipe soil coupling model in the stratum settlement area is established to investigate the effects of stratum settlement, pipe wall thickness, internal pressure, and pipe steel grade on the pipe’s buckling mode and mechanical properties. The results show that the axial tensile strain and compressive strain of the pipe are concentrated in the settlement transition zone under the action of stratum settlement. When the settlement is small, the surface strain of the pipe is wavy, while the pipe produces local buckling when the settlement is large. Under the same working conditions, thin-walled pipes are prone to buckling failure, whereas thick-walled pipes appear corrugated strain distribution. Additionally, with the increasing of internal pressure, the buckling of the pipe gradually weakens. The buckling degree of high-grade steel pipes is smaller. References | Related Articles | Metrics

Automation Technique and Computer Technology

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A secondary voltage control method for the microgrid considering stochastic communication delay FENG Yi-wei, MA Jing 2024, 50 (3):  69-76.  Abstract ( 50 )   PDF (1363KB) ( 30 )   Save A distributed cooperative consensus algorithm is presented for the secondary voltage recovery problem of the islanded microgrid with stochastic communication delay. Firstly, the islanded microgrid model is established, and the secondary voltage recovery mechanism of microgrid system with stochastic communication time delay is qualitatively analyzed. The distributed observer is introduced to estimate the system states, and a distributed consensus cooperative control strategy is proposed. Then, based on Lyapunov stability theory and Schur’s complement principle, the sufficient conditions of asymptotic convergence for the stochastic communication time-varying delay system with zero and non-zero external inputs are obtained. The proposed control method improves the anti-disturbance capability of the islanded microgrid system and meets the stability and reliability requirements of the closed-loop system. Finally, the performance of the microgrid system is verified by simulation, which proves the feasibility and correctness of the theorem. References | Related Articles | Metrics

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Bipartite consensus of multi-agent systems triggered by distributed events WANG Jun, WEI Ya-ping 2024, 50 (3):  77-83.  Abstract ( 47 )   PDF (3605KB) ( 93 )   Save This paper deals with the problem of bipartite consistency in multi-agent control systems based on distributed event triggering. A coherent control protocol with a cooperative and competitive topology for achieving consensus among multi-agent systems is proposed, aiming to drive the system to converge to states with binary disagreement yet identical magnitudes. On the basis of graph theory and matrix theory, the problem of binary consensus in multi-agent systems is reformulated into a stability issue for closed-loop error systems. By establishing an appropriate Lyapunov function, the asymptotic stability of the closed-loop error system is validated. Moreover, event-triggering conditions are introduced for each agent to reduce control update frequencies and communication resource consumption. Additionally, it is demonstrated that there exists a strict lower bound for the time intervals between successive triggers for neighboring agents, thereby preventing Zeno phenomena. Finally, through simulation instances, the feasibility and effectiveness of the proposed method are verified. References | Related Articles | Metrics

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Mechanical resonance suppression method for servo system based on IP control and load acceleration feedback SUN Yan, BAO Guang-qing, DU He-xuan 2024, 50 (3):  84-89.  Abstract ( 46 )   PDF (1319KB) ( 11 )   Save When the bandwidth of a servo system covers the natural frequency of the transmission device, it is easy to cause mechanical resonance in the system, which seriously affects the dynamic performance and control accuracy of the system. To solve this problem, a resonance suppression strategy of a servo system based on IP control with load-side acceleration state feedback is proposed in this paper. By using IP control in the speed loop, the overshoot of the system is effectively reduced, while the acceleration feedback is introduced in the current loop to increase the degree of freedom of pole placement. On this basis, according to the pole assignment method with the same damping coefficient and taking the optimal damping ratio as the design goal, the value range of the key parameters of the system controller and the state feedback gain are discussed.Finally, the effectiveness of the proposed control method is verified by simulation. References | Related Articles | Metrics

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Volume-preserving 2D-3D point set registration algorithm based on Lie group representation YU Ying, CAI Chen-wei, YING Shi-hui, LI Ce 2024, 50 (3):  90-97.  Abstract ( 41 )   PDF (2142KB) ( 9 )   Save The aim of 2D-3D point set registration is to find the optimal transformation and correspondence between 3D source point set and 2D target projection point set. In order to obtain the closed-form solution to the registration problem and avoid the volume degradation caused by projection, a volume-preserving 2D-3D point set registration algorithm based on Lie group representation was proposed. Firstly, considering the non-commutativity of the projection matrix and the rotation matrix, the Lie group representation is introduced to formalize the registration problem into an optimization problem based on Lie group. The Lie group optimization problem is transformed into a computationally quadratic programming problem by the local linearization method. Secondly, in order to avoid volume degradation, the projection of 3D transformed point set is constrained to have the same volume as that of 2D target point set. In order to facilitate calculation, the Jensen-Bregman LogDet divergence is introduced as a volume-preserving regularization term, converting the volume difference calculation into a covariance matrix difference calculation. Subsequently, a complete and solvable iteration strategy is developed by alternately solving for the correspondence and the optimal transformation. Finally, comparative experiments and ablation experiments on two classical data sets verify the accuracy and effectiveness of the proposed approach. References | Related Articles | Metrics

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Design and implementation of faster-than-Nyquist visible light communication system CAO Ming-hua, ZHANG Jia-wei, WANG Xiao-bing, ZHOU Hong-tao ZHANG Yue, WANG Hui-qin 2024, 50 (3):  98-103.  Abstract ( 45 )   PDF (2242KB) ( 39 )   Save In order to improve the data rate of visible light communications (VLC), a faster-than-Nyquist (FTN) VLC system is proposed based on the faster-than-Nyquist communication theory. Red light emitting diode (LED) with the wavelength of 660 nm, field programmable gate array (FPGA), digital/analog (D/A) conversion chip, filter chips, photo-diodes (PD), and related modules are employed to build the transceiver circuits with intensity modulation/direct detection. The proposed system can effectively improve the transmission rate of the VLC system without significantly increasing the system’s complexity and cost. Performance tests show that the system discussed here can realize FTN signal transmission at 1 Mbit/s, which is about 20% higher than the conventional Nyquist communication system with the same electronic and optical components. References | Related Articles | Metrics

Architectural Sciences

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Finite element analysis of seismic behavior of steel plate shear wall structure with PEC column (weak axis connection) ZHANG Ji-hong, WU Hong-kai, YIN Zhan-zhong, FENG Da-zhe, Zhao Shuai-peng 2024, 50 (3):  104-110.  Abstract ( 41 )   PDF (5419KB) ( 30 )   Save In order to study the seismic performance of steel plate shear wall structures (weak axis connection) with partially encased concrete composite columns, a numerical simulation of one steel plate shear wall structure with H-shaped edge column and five steel plate shear wall structures with PEC column (weak axis connection) under cyclic loading was conducted using the finite element software ABAQUS. The stress distribution, failure mode, hysteretic curve, energy dissipation performance, skeleton curve, and stiffness degradation curve of the structure are obtained. Additionally, a test of a steel plate shear wall structure with a PEC column (weak axis connection) was performed to validate the finite element model. The analysis shows that in the steel plate shear wall structure (weak axis connection), taking the PEC column as the edge frame column of the shear wall effectively restrains the steel plate shear wall after buckling, making it give full play to the post buckling performance, and significantly improving the lateral stiffness, bearing capacity, and energy dissipation performance of the whole structure. References | Related Articles | Metrics

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The study on spatial evolution and mechanism of urban transportation facilities in Lanzhou Belt City based on POI CHAI Zong-gang, LI Chun-xia 2024, 50 (3):  111-122.  Abstract ( 54 )   PDF (8137KB) ( 18 )   Save Based on the POI data of urban traffic facilities in Lanzhou Central City from 2011 to 2022, this paper analyzes the spatial evolution:spatial form, directional distribution and hot and cold spots, and studies the influencing mechanism. The results show that: the urban transportation facilities show the characteristics of “east dense west” and the degree of agglomeration is enhanced, the urban transportation facilities and parking facilities change from “single core” to “single core, multiple scattered points coexist”, and the public transportation facilities change from “one main once” to “one main many times” and multiple scattered points appear at the edge. Urban transportation facilities are distributed in the direction of “northwest-southeast”, and the center of gravity experiences an offset track of “southeast-northwest-northeast”, with a trend of spreading to the northwest and northeast, and the distribution of public transportation facilities is more dispersed than parking facilities. The hot spots of urban traffic facilities and parking facilities in the Chengguan District change from scattered points along the road to linear distribution along the road, and finally show Dongfanghong Square as the core, and the other three districts change from scattered points along the road to linear distribution; The hot spots of public transportation facilities are relatively dispersed and linearly distributed along the road. The constraints of the “humanity-geography” environment, the regulation of government planning, and the promotion of the perfect transportation network jointly affect the spatial evolution of urban transportation facilities. References | Related Articles | Metrics

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Research on influence of deep foundation pit excavation on adjacent expressway and stress and deformation of support system ZHANG Hong-ying, LI Xu-sheng, YUAN Hua-zhi,GAO Hong 2024, 50 (3):  123-129.  Abstract ( 70 )   PDF (4999KB) ( 37 )   Save The rapid development of urban infrastructure has led to the numerous foundation pits close to highways, posing new challenges for deformation control of both the foundation pits and the adjacent expressways. To ensure the safety of expressways adjacent to deep foundation pits, this studyuses the finite element method to establish a three-dimensional numerical simulation model considering the vehicle load based on the project overview, construction methods, and reinforcement measures of a deep foundation near an expressway. Then the displacement of the highway pavement, the displacement and the internal force of the supporting structure during and after the excavation were systematically analyzed. The results reveal that there is a phenomenon of uplift on both sides of the middle settlement. The horizontal displacement of the pavement and supporting structure towards the direction of the foundation pit is found, and the supporting structure present a “float up” as a whole. The middle beams of the supporting structures are under compression, while the side beams are under tension, with the compressive forces significantly exceeding the tensile forces. Increasing the supporting density can effectively reduce the displacement of both the pavement and the supporting structure. References | Related Articles | Metrics

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Research on schemes of shield direct cutting launching WEN Sen, ZHANG Guo-jian, LIU Jun-jie, KONG Qing-mei 2024, 50 (3):  130-136.  Abstract ( 46 )   PDF (5632KB) ( 23 )   Save With the development of shield construction technology, the use of shield direct cutting launching for tunnel initiation has become increasingly prevalent.In shield tunneling construction, the launching is an important link that is prone to accidents. Compared to traditional manual chiseling of the tunnel door, the cutting disc directly cuts the tunnel door during direct cutting launching, avoiding the occurrence of a free surface on the soil mass of the tunnel face, thereby reducing.Taking the subway shield tunnel engineering in Zhengzhou shield direct cutting launching as a case study, the finite element software Midas GTS NX was employed to the effects of the tunnel portal break and dynamic tunneling shield in retaining structure deformation, deformation of soil around the pipe deformation and so on, verifying the shield end cut the rationality of the initial solution. In order to verify the reliability of numerical simulation, a comparative analysis was conducted between the numerical calculation results and field monitoring data. The comparison showed consistent variation results, indicating that the results of numerical simulation are reasonable. References | Related Articles | Metrics

Scientific

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Enumeration of the partial Motzkin paths YANG Sheng-liang, WANG Nan 2024, 50 (3):  137-142.  Abstract ( 41 )   PDF (542KB) ( 39 )   Save A partial Motzkin path of length n is a lattice path from (0,0) to (n,k), which run through the integer points, consisting of up steps U=(1,1), down steps D=(1,－1) and horizontal steps H=(1,0), and it never goes below the x-axis. The number of Motzkin paths from (0,0) to(n,0) is called the n-th Motzkin number. The generating function of Motzkin numbers and the representation of the Riordan matrix of the number of partial Motzkin paths are obtained by using the kernel method. Finally, the generating functions of partial Motzkin paths with restricted height are given by using recurrence relations and the linear algebraic method. Some relevant examples are presented here. References | Related Articles | Metrics

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An element subdivision method for singular domain integrals based on feature partition technique JIA Zhi-chao, WANG Fu-shun, GUO Qian-jian, YUAN Wei, WEI Zheng 2024, 50 (3):  143-150.  Abstract ( 42 )   PDF (3947KB) ( 29 )   Save Aiming at the difficulty of solving the singular integrals by traditional algorithms, an adaptive element subdivision method for singular domain integrals based on feature partition technique is presented. The element subdivision method is based on binary-tree data structure, which is applicable to arbitrary shape volume elements with arbitrary locations of the source point. By using the techniques of the binary-tree subdivision scheme, construction of the projection cavities and the cavity projection algorithm, well-shaped patches can be obtained for singular domain integrals. Numerical examples demonstrate that the proposed method has much better accuracy and efficiency than conventional methods. References | Related Articles | Metrics

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A Hilbert-type inequality with a discrete fractional kernel YOU Ming-hui, DONG Fei, YANG Bi-cheng 2024, 50 (3):  151-155.  Abstract ( 39 )   PDF (485KB) ( 20 )   Save By introducing several positive parameters, a new fractional discrete kernel function is constructed. By means of the method of weight coefficients, a double Hilbert series inequality is established, and the constant factor of the newly obtained inequality is proved to be the best possible. Furthermore, based on the rational fraction expansion of the cosecant function, it is also proved that the optimal constant factor can be represented by the cosecant function. At last, by assigning some specific values to the parameters, some previously known results are obtained, and some new Hilbert-type inequalities with special kernel functions are also presented at the end of the paper. References | Related Articles | Metrics

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The 2-distance sum distinguishing total colorings for middle graphs of some special classes of graphs WANG Tong-xin, YANG Chao, YAO Bing 2024, 50 (3):  156-161.  Abstract ( 45 )   PDF (605KB) ( 33 )   Save To further study the problem of 2-distance sum distinguishing total coloring, according to the structural properties of middle graphs, by constructing coloring functions and taking advantage of the methods of combinatorial analysis, the 2-distance sum distinguishing total chromatic numbers for middle graphs of path, cycle, star, fan, wheel, double star and wheel-ring graph are obtained. References | Related Articles | Metrics

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New conditions for generalized strictly diagonally dominant matrices ZHANG Jin-song 2024, 50 (3):  162-166.  Abstract ( 47 )   PDF (476KB) ( 35 )   Save By using elements of matrices, some new conditions for identifying generalized strictly diagonally dominant matrices are obtained, which enlarge the identification range. Numerical examples are presented. References | Related Articles | Metrics

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Some properties of complex structures on compact homogenous space G/T DU Cai-yu, WANG Yu 2024, 50 (3):  167-172.  Abstract ( 43 )   PDF (500KB) ( 20 )   Save Given a connected simply-connected s-step real nilpotent Lie group G with a left invariant integrable almost complex structure J and a lattice T of maximal rank of the Lie group G, the existence of a nilpotent complex structure on the compact homogeneous spaceG/T is considered. It is shown in this paper, through the use of inductive methods, that the complex structure J can induce an integrable complex structure $\widetilde{J}$ on the compact homogeneous spaceG/T, and that $\widetilde{J}$ is nilpotent. References | Related Articles | Metrics