期刊：
Journal of Sea Research,2024年198:102474 ISSN：1385-1101
作者机构：
[Zhiping Lian] Art and Design College, International Education College, Hunan City University, Yiyang 413000, China
关键词：
A priori-neural-learning-based networks;Marine economic degree growth;Multivariate estimation;Marine art industry;Synergistic development
摘要：
Marine and port economy estimation is conducive to the understanding of the development law of marine economy degree. This study proposes a neural-learning network estimation model of the marine economy degree based on a priori architectural knowledge and adopts time-combined class array columns and multivariate modeling methods to estimate the indicators reflecting the development level of the marine economy degree in the ZJP region. The study adopts the PK_NN multivariate modeling method, taking cargo transportation volume, cargo turnover, cargo carrying value of ports near the sea, foreign trade throughput, port container throughput, and port container throughput as multivariate model inputs, and compared with the other modeling methods, the model of the time combination class array columns of type GM_11, which has a better comprehensive performance. Finally, the PK_NN time-combined class array column model is used to estimate the development level of the marine economy in the ZJP region near the seaport from 2011 to 2020, and the results show that the estimated value of the marine economy in the ZJP region is close to the actual planning value of the ZJP region. The algorithm was applied to estimate the economic degree curves of the five near-seaport areas of ABCDE under different harbor head construction art modes, and the results showed that the relative value error of the estimation was controlled between 4% and 10%, and the fluctuation ranges of each month's specific growth value area estimation were comparable. This proves the effectiveness and accuracy of the a priori marine neural-learning-based network algorithm in this paper.
作者机构：
[Luo, Qiao; Yu, Hongbing] Hunan City Univ, Coll Architecture & Urban Planning, Yiyang 413000, Peoples R China.;[Luo, Qiao; Yu, Hongbing] Hunan City Univ, Coll Architecture & Urban Planning, Lab Key Technol Digital Urban Rural Spatial Planni, Yiyang 413000, Peoples R China.;[Li, Yong] Chinese Acad Sci, Inst Atmospher Phys, State Key Lab Atmospher Boundary Layer Phys & Atmo, Beijing 100029, Peoples R China.;[Jiang, Shufang; Cao, Xueyou] Forestry Bur Yiyang City, Yiyang 410004, Peoples R China.
通讯机构：
[Li, Y ] C;Chinese Acad Sci, Inst Atmospher Phys, State Key Lab Atmospher Boundary Layer Phys & Atmo, Beijing 100029, Peoples R China.
关键词：
South Dongting Lake Nature Reserve;blue space;green space;precipitation;air temperature
摘要：
In recent years, the water level of the Dongting Lake (DTL) has been continuously low, and the wetland area and landscape pattern have changed significantly. Considering the obvious spatial heterogeneity of water regime changes in different waters of the DTL, this paper takes two core areas of the South Dongting Lake Nature Reserve (SDLNR) as study areas and analyzes the spatial distribution characteristics of the wetland blue–green landscape patterns by using remote sensing image data and hydrological and meteorological data. The multi-scale correlation between runoff, precipitation, temperature, and evapotranspiration in the SDLNR was studied via cross-wavelet transform analysis. The results show the following: (1) The change in the blue–green spatial patterns in different regions in different periods is inconsistent, and this inconsistency is related to the topography, climate, and human activities in each region; (2) there are seasonal fluctuations in precipitation, air temperature, and evapotranspiration in the SDLNR. Among them, the annual mean temperature shows a rising trend and passes the significance test with 95% confidence, while the annual mean precipitation and annual mean evapotranspiration show no significant change trend; and (3) our Pearson correlation analysis and cross-wavelet change results show that precipitation and temperature are strongly correlated with runoff, with a resonance period of 8–16 months, while the correlation between evapotranspiration and runoff is not significant. We recommend that policymakers establish an effective early warning system and make plans to store water through micro-terrain transformation in possible climate change treatments and strategies.
作者机构：
Hunan Provincial Key Laboratory of High Efficiency and Precision Machining of Difficult-to-Cut Material, Hunan University of Science and Technology, Xiangtan, Hunan 411201, China;School of Mechanical Engineering, Hunan University of Science and Technology, Xiangtan, Hunan 411201, China;College of Automotive Engineering, Hunan Electrical College of Technology, Xiangtan, Hunan 411101, China;School of Mechanical and Electrical Engineering, Hunan City University, Yiyang, Hunan 413000, China;[Shichun Li; Gang Xiao; Hua Zhang] Hunan Provincial Key Laboratory of High Efficiency and Precision Machining of Difficult-to-Cut Material, Hunan University of Science and Technology,Xiangtan, Hunan 411201,China<&wdkj&>School of Mechanical Engineering, Hunan University of Science and Technology,Xiangtan, Hunan 411201,China
通讯机构：
[Shichun Li] H;Hunan Provincial Key Laboratory of High Efficiency and Precision Machining of Difficult-to-Cut Material, Hunan University of Science and Technology, Xiangtan, Hunan 411201, China<&wdkj&>School of Mechanical Engineering, Hunan University of Science and Technology, Xiangtan, Hunan 411201, China
摘要：
In order to study the virtual simulation of weld morphology for V-groove multi-layer welding, the prediction of characteristic parameters for weld morphology was realized by constructing the neural network models between the characteristic parameters and process parameters of different layers. At the same time, the virtual models of different layers were established according to the characteristic parameters of weld morphology and the structure parameters of V-groove. Combined with the prediction model and the virtual model, the process parameters were associated with the weld morphology, and the virtual simulation of weld morphology was realized. In the process of establishing the virtual model, first of all, the virtual model of root weld is established. Then, the virtual model of filling layer is established based on the root layer, and the virtual model of weaving layer is established based on the filling layer. Finally, validation experiments were carried out to verify the accuracy of the model. Verification results show that the prediction model can effectively predict the characteristic parameters of each layer, and the average relative errors of melting depth and width were less than 8%. The virtual simulation morphology has a high consistency with the actual morphology, and the average relative error of cross section area was less than 10%.
期刊：
International Journal of Reasoning-based Intelligent Systems,2024年15(3-4):323-331 ISSN：1755-0556
作者机构：
1. Academy of Music and Dance, Hunan City University, Yiyang 413000, Hunan, China;2. Academy of Music, Jianghan University, Wuhan 430056, Hubei, China
摘要：
Because the collaborative filtering algorithm cannot achieve accurate matching, a personalised music resource recommendation algorithm based on category similarity is proposed. The user preference type parameters are obtained by the modelling and analysis method of knowledge graph and the personalised preference judgement model is established according to the type parameters. The feature registration algorithm is used to mine the personalised features of music resources, and the homomorphic reliability of the personalised scores is analysed to build a joint parameter matching model of music resources. Finally, through the analysis of category similarity characteristics, the adaptive statistical analysis of music resources is carried out, and the personalised feature parameters of music resources are extracted to achieve personalised recommendation of music resources. The simulation results show that the minimum satisfaction of the method in the optimal state is 92.7%, the resource holding level is always above 92%, and the recommended accuracy is 98.9%, which shows that the method in this paper is more practical.
摘要：
Kaempferol (KA), which is a biologically active natural polyphenol compound with considerable medicinal value, can be used to fight various diseases. Herein, a beta-cyclodextrin/fullerene-graphene oxide/Nickel-metal-organic framework (beta-CD/C-60-GO/Ni-MOF) composite-based electrochemical sensor was developed to detect KA; the composite was characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron (XPS) spectroscopy. The biocompatibility and host-guest recognition performance of beta-cyclodextrin (beta-CD); the porosity and the catalytic performance of the nickel-metal-organic framework (Ni-MOF); and the excellent electrical conductivity of fullerene-graphene oxide (C-60-GO) work together to considerably improve the detection performance of the sensor for KA. The sensor has an extensive linear range (0.5-50 mu M) and a low detection limit (58 nM) with an electrochemically active specific surface area of 0.0971 cm(2); furthermore, the redox mechanism of KA in the sensor is explained. For the detection of actual natural samples of broccoli containing KA, satisfactory recovery rates and accuracy were observed; the recovery rate was 96.4 %-101.1 %.
作者机构：
[Ning Liu; Yi Li; Yiwen Hu] College of Meteorology and Oceanography, National University of Defense Technology, Changsha, 410003, China;High Impact Weather Key Laboratory of CMA, Changsha, 410003, China;[Xin Fang] School of Municipal and Geomatics Engineering, Hunan City University, Yiyang, 413000, China;National Research Council of Italy, Institute of Methodologies for Environmental Analysis (IMAA), Contrada S. Loja snc, 85050, Tito Scalo, PZ, Italy;CommSensLab, Dept. of Signal Theory and Communications, UPC, 08034, Barcelona, Spain
通讯机构：
[Yi Li] C;College of Meteorology and Oceanography, National University of Defense Technology, Changsha, 410003, China
摘要：
Satellite-based aerosol optical depth (AOD) products are commonly used in various aerosol-related studies, such as aerosol pollution mapping and aerosol-climate interactions. However, these satellite AOD products often suffer from significant missing gaps due to cloud cover and limitations in the retrieval algorithm. To address this issue, some studies take advantage of real-time seamless simulation of numerical models and successfully fill in these gaps by establishing a regression relationship between satellite AOD and numerical model AOD. However, these previous studies usually use satellite AOD retrievals as the regression target, which limits the accuracy of the imputation results by the original accuracy of satellite AOD retrievals and also consumes a considerable amount of time. To overcome these limitations, this study proposes a spatiotemporal imputation model called Bi-ConvRNN, which combines convolutional neural networks (CNN) and bidirectional recurrent neural networks (Bi-RNN). The model takes both satellite AOD retrievals and numerical model AOD data as input and utilizes the weighted mean squared error (MSE) loss function of multiple AOD datasets, e.g., ground-based data, satellite retrievals, and numerical simulation, as the optimization target to improve the imputation accuracy. The proposed model is evaluated using hourly COMS GOCI AOD products. In the independent test set, the AOD results generated by the Bi-ConvRNN model in the region containing GOCI AOD retrievals can break the accuracy of original GOCI AOD products with the accuracy improved from R2 = 0.70 [RMSE = 0.15] to R2 = 0.84 [RMSE = 0.11], and the filling accuracy, e.g. R2 = 0.79, [RMSE = 0.14], in the region without GOCI AOD retrievals are still better than those of the original GOCI AOD retrievals. Additionally, the Bi-ConvRNN model demonstrates satisfactory filling efficiency, requiring only 0.12 s to fill in the missing gaps of hourly GOCI AOD products per day. These results highlight the efficiency and reliability of the proposed model in filling the gaps in satellite AOD products, and the filled AOD results have great potential for further aerosol-related research.
作者：
Yi Su;Xiaoyun Peng;Haiou Li;Wenzhen Ku;Ruozhong Wang;...
期刊：
Plants-Basel,2024年13(6):899- ISSN：2223-7747
通讯作者：
Haiou Li<&wdkj&>Langtao Xiao
作者机构：
Authors to whom correspondence should be addressed.;[Yi Su; Ruozhong Wang] Hunan Provincial Key Laboratory of Phytohormones and Growth Development, Hunan Agricultural University, Changsha 410128, China;Hunan Provincial Key Lab of Dark Tea and Jin-Hua, College of Materials and Chemical Engineering, Hunan City University, Yiyang 413000, China;[Xiaoyun Peng; Wenzhen Ku] Hunan Provincial Key Lab of Dark Tea and Jin-Hua, College of Materials and Chemical Engineering, Hunan City University, Yiyang 413000, China<&wdkj&>Hunan Provincial Key Laboratory of Phytohormones and Growth Development, Hunan Agricultural University, Changsha 410128, China;[Haiou Li; Langtao Xiao] Authors to whom correspondence should be addressed.<&wdkj&>Hunan Provincial Key Laboratory of Phytohormones and Growth Development, Hunan Agricultural University, Changsha 410128, China
通讯机构：
[Haiou Li; Langtao Xiao] A;Authors to whom correspondence should be addressed.<&wdkj&>Hunan Provincial Key Laboratory of Phytohormones and Growth Development, Hunan Agricultural University, Changsha 410128, China
摘要：
Axillary bud outgrowth, a key factor in ratoon rice yield formation, is regulated by several phytohormone signals. The regulatory mechanism of key genes underlying ratoon buds in response to phytohormones in ratoon rice has been less reported. In this study, GR24 (a strigolactone analogue) was used to analyze the ratooning characteristics in rice cultivar Huanghuazhan (HHZ). Results show that the elongation of the axillary buds in the first seasonal rice was significantly inhibited and the ratoon rate was reduced at most by up to 40% with GR24 treatment. Compared with the control, a significant reduction in the content of auxin and cytokinin in the second bud from the upper spike could be detected after GR24 treatment, especially 3 days after treatment. Transcriptome analysis suggested that there were at least 742 and 2877 differentially expressed genes (DEGs) within 6 h of GR24 treatment and 12 h of GR24 treatment, respectively. Further bioinformatics analysis revealed that GR24 treatment had a significant effect on the homeostasis and signal transduction of cytokinin and auxin. It is noteworthy that the gene expression levels of OsCKX1, OsCKX2, OsGH3.6, and OsGH3.8, which are involved in cytokinin or auxin metabolism, were enhanced by the 12 h GR24 treatment. Taken overall, this study showed the gene regulatory network of auxin and cytokinin homeostasis to be regulated by strigolactone in the axillary bud outgrowth of ratoon rice, which highlights the importance of these biological pathways in the regulation of axillary bud outgrowth in ratoon rice and would provide theoretical support for the molecular breeding of ratoon rice.
作者：
Wang, Xinzhong;Li, Linshu;Xiang, Yi;Wu, Yuexing;Wei, Mei
期刊：
Frontiers in Materials,2024年10 ISSN：2296-8016
通讯作者：
Wang, XZ
作者机构：
[Li, Linshu; Wang, XZ; Wang, Xinzhong; Wu, Yuexing; Xiang, Yi] Hunan City Univ, Sch Civil Engn, Yiyang, Peoples R China.;[Wei, Mei] Hunan Arts & Crafts Vocat Coll, Sch Digital Arts, Yiyang, Peoples R China.
通讯机构：
[Wang, XZ ] H;Hunan City Univ, Sch Civil Engn, Yiyang, Peoples R China.
关键词：
concrete-filled steel tube;basalt fiber;short columns;finite element analysis;bearing capacity;ductility coefficient
摘要：
With rapid economic and social development, both concrete-filled steel tube (CFST) composite structures and basalt fiber (BF) have been widely applied in the field of civil engineering. To investigate the laws and characteristics of the influence of chopped BF on the mechanical properties of CFST columns and further promote the application of BF in CFST structures, the axial compressive bearing capacity test of 18 CFST short columns was carried out, and the influence of BF of different lengths on their structural mechanical properties was analyzed. The test results were compared with the theoretical calculation results and the finite element analysis results to verify the reasonableness of the test results. The results reveal that the axial compressive bearing capacity of the CFST short column after adding BF is significantly improved compared to the ordinary CFST short column, in which the bearing capacity and the ductility coefficient are increased by approximately 8.1% and 31.6%, respectively, on average. In addition, changing the length of BF has less effect on the bearing capacity of CFST short columns, the rate of increase in bearing capacity decreases with an increase in the steel ratio of CFST, and the coefficient of ductility increases with the increase in the steel ratio.
关键词：
Asphalt mixture;Mesoscopic analysis;Skeleton evolution;Aggregate contact;Particle movement;Discrete element method
摘要：
The aggregate skeleton is the intrinsic core of asphalt mixtures for load transfer, which is quite different under various gradations. For evaluating the loading characteristics of the aggregate skeleton, this research combined the 3D blue -ray scanning technology and discrete element method (DEM) to establish the numerical models of different graded asphalt mixtures considering the real aggregate morphology. A linear parallel bond model was used to simulate the adhesion effect of asphalt, and the uniaxial compression numerical simulation was verified by indoor tests. In addition, the contact force, contact number, anisotropy, and rotation angle were used to evaluate the aggregate skeleton evolution under uniaxial compression loading. Furthermore, the contribution of each grade aggregate in the gradation to the skeleton structure was analyzed. Results show that the average contact force is higher in large -size aggregates above 9.5 mm, which exhibit greater load transfer efficiency. Moreover, 4.75-9.5 mm size aggregates combine the functions of bearing and filling, and its role is significantly affected by the gradation. It is also found that the internal skeleton structure can be optimized and adjusted under stress. The contact numbers of different graded mixtures follow a close decrease, and the strong contacts are mostly provided by coarse aggregates above 4.75 mm. The anisotropy development of aggregate skeleton contact force is induced by the stress, and the deviator fabric of asphalt mixtures show a good linear positive correlation with the uniaxial compressive strength (UCS). Besides, fine aggregates exhibit greater cumulative rotation angle and instability effect, it is feasible to detect asphalt mixture deformation by the rotation angle of particles.
期刊：
Journal of Affective Disorders,2024年347:645-655 ISSN：0165-0327
通讯作者：
Xiang, YH;Li, XJ
作者机构：
[Xiang, Yanhui] Hunan City Univ, Teacher Educ Coll, Yiyang, Peoples R China.;[Cao, Rong; Xiang, Yanhui] Hunan Normal Univ, Cognit & Human Behav Key Lab Hunan, Changsha, Peoples R China.;[Cao, Rong; Xiang, Yanhui] Hunan Normal Univ, Dept Psychol, Changsha, Peoples R China.;[Li, Xiaojun] Nanjing Xiaozhuang Univ, Tao Xingzhi Res Inst, Nanjing, Peoples R China.;[Xiang, Yanhui; Xiang, YH] Hunan Normal Univ, Dept Psychol, Changsha 410081, Peoples R China.
通讯机构：
[Xiang, YH ] H;[Li, XJ ] N;Hunan Normal Univ, Dept Psychol, Changsha 410081, Peoples R China.;Nanjing Xiaozhuang Univ, Tao Xingzhi Res Inst, Nanjing 210038, Peoples R China.
关键词：
Adolescent depression;Country income level;Cross-national;Geographical region;Meta-analysis;Parental education level;Socioeconomic status
摘要：
Adolescent depression, as a common problem, has always been the focus of attention and research. However, no consistent conclusion has been drawn on its relationship with parental education level. Therefore, this study used meta-analysis and dose-response analysis techniques to explore the overall relationship between the two, and further explore the moderating factors affecting the relationship between the two through subgroup analysis and meta-regression analysis. After a literature search and screening, a total of 22 literatures were included, including 634,821 adolescents aged 9-25, distributed in 10 countries. The results showed that: (1) Overall parental education level was negatively correlated with adolescent depressive symptoms (RR=0.88. p < 0.001), and there was a dose-response relationship between the two. (2) Geographical location (p=0.002<0.05) and national economic development (p=0.03<0.05) significantly moderated and affected the association between parental education level and adolescent depression, thus presenting a global inconsistency. The results of this study provide a more accurate conclusion on the relationship between parental education and adolescent depression to some extent, highlight the importance and necessity of considering family, economic and cultural factors when studying and solving adolescent depression problems, and guide us to pay more attention to the cross-regional and cross-cultural differences in adolescent depression problems.
作者机构：
[Ruoli Shi] School of Architecture and Planning, Yunnan University, Kunming 650504, China;[Zongyun Mo] School of Architecture and Civil Engineering, Anhui Polytechnic University, Wuhu 241000, China;[Zhijian He] School of Physics and Chemistry, Hunan First Normal University, Changsha 410205, China;Authors to whom correspondence should be addressed.;Sinohydro Engineering Bureau 8 Co., Ltd., Changsha 410004, China
通讯机构：
[Bing Cao; Fanjun Ma] A;Authors to whom correspondence should be addressed.<&wdkj&>Sinohydro Engineering Bureau 8 Co., Ltd., Changsha 410004, China<&wdkj&>Authors to whom correspondence should be addressed.<&wdkj&>School of Architecture and Civil Engineering, Anhui Polytechnic University, Wuhu 241000, China
摘要：
To study the mechanical performance of bolted connections with different structural forms of reinforced rings, based on the results of monotonic loading tests on two bolted connections between a concrete-filled steel tubular column and a steel beam with an outer reinforcing ring, this article uses ABAQUS v.2020 software to establish a three-dimensional refined finite element analysis model of such connections using appropriate constitutive models for concrete and steel. Subsequently, the effect of the dimensions of the steel beam, reinforcing ring, and cover plate on the load-bearing properties and the failure mechanism of the connections is investigated, and the numerical model is consistent with the verification test results. Then, the numerical simulations comparing bolted exterior reinforced rings under seven different construction measures (i.e., number of bolts, stiffeners) based on a conventional welded exterior reinforced rings with rigid connections (i.e., CGJ) are standardized. The research results indicate that when four rows of bolts are introduced on exterior reinforced rings, the web of steel beam is welded with stiffeners, and the top and bottom reinforced rings are also added with stiffeners; this bolted connection with an external reinforcing ring (i.e., GZ-7) can achieve the rigidity and load-bearing capacity of a fully welded external reinforcing ring rigid connection. At the same time, the reinforcing ring plate is bolted to the flange of the steel beam, and the force transmission path at the connection is changed to avoid the brittle fracture easily caused by the welded flange joints. It is also in line with the development trend of sustainable construction of “assembly” and “disassembly”.
作者：
Ming Xiao*;Lihua Chen;Haoxiong Feng;Zhigao Peng;Qiong Long
期刊：
Archives of Computational Methods in Engineering,2024年:1-25 ISSN：1134-3060
通讯作者：
Ming Xiao
作者机构：
[Ming Xiao; Lihua Chen; Haoxiong Feng; Zhigao Peng; Qiong Long] College of Civil Engineering, Hunan City University, Yiyang, China
通讯机构：
[Ming Xiao] C;College of Civil Engineering, Hunan City University, Yiyang, China
摘要：
This paper investigates the implementation of a Multi-Objective Optimization technique for improving public transportation route planning in the setting of smart cities. Recognizing the difficulties of urban mobility, our technique incorporates a variety of criteria, including traffic patterns, cost-effectiveness, and environmental impact, to create an efficient route design system. The research applies complex algorithms to overcome the issues present in existing route planning procedures, using real-world data sources such as GPS data and traffic reports. We illustrate the efficacy of our strategy in boosting time efficiency, lowering costs, and decreasing environmental footprints via extensive case studies. The assessment measures used emphasise the suggested system’s advantages over current techniques. The debate digs into the larger implications for smart city development, recognising limits and providing possibilities for further study. This study adds vital insights and practical answers to the developing subject of smart city transportation, providing a solid basis for the continuing growth of urban mobility.
作者机构：
[Shuang-shuang Zhou] School of Science, Hunan City University, Yiyang, China;[Muhammad Ijaz Khan] Department of Mechanical Engineering, Prince Mohammad Bin Fahd University, Al-Khobar, Kingdom of Saudi Arabia;[Sami Ullah Khan] Department of Mathematics, Namal University, Mianwali, Pakistan;[Sumaira Qayyum] Department of Mathematics, Quaid-I-Azam University 45320, Islamabad, Pakistan
通讯机构：
[Muhammad Ijaz Khan] D;Department of Mechanical Engineering, Prince Mohammad Bin Fahd University, Al-Khobar, Kingdom of Saudi Arabia
关键词：
heat generation;surface reaction;CNTs based nanofluid;stretching/shrinking sheet;thermal radiation
摘要：
The investigation endorsed the convective flow of Carreau nanofluid over a stretched surface in presence of entropy generation optimization. The novel dynamic of viscous dissipation is utilized to analyze the thermal mechanism of magnetized flow. The convective boundary assumptions are directed in order to examine the heat and mass transportation of nanofluid. The thermal concept of thermophoresis and Brownian movements has been re-called with the help of Buongiorno model. The problem formulated in dimensionless form is solved by NDSolve MATHEMATICA. The graphical analysis for parameters governed by the problem is performed with physical applications. The affiliation of entropy generation and Bejan number for different parameters is inspected in detail. The numerical data for illustrating skin friction, heat and mass transfer rate is also reported. The motion of the fluid is highest for the viscosity ratio parameter. The temperature of the fluid rises via thermal Biot number. Entropy generation rises for greater Brinkman number and diffusion parameter.
通讯机构：
[Zhang, L ] H;Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;Hunan Univ Technol, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Peoples R China.
关键词：
boulder and hard rock environment;GPR;wavelet scale energy spectrum;wavelet packet energy;time-frequency characteristics
摘要：
The hard rocks in the stratum can pose safety risks and hinder the progress of urban underground tunnel construction using shield and jacking methods, thereby reducing construction efficiency and increasing construction costs. This paper utilizes wavelet scale energy spectrum, wavelet packet theory and statistical methods to conduct research on the detection of special geological formations such as hard rocks and voids, as well as the analysis of their signal time-frequency characteristics based on the ground-penetrating radar (GPR) technique. On the basis of calibrating the permittivity of different types of rock blocks, we established a forward model for detecting hard rocks and voids, and the simulated signals were analyzed in the time and frequency domains. Subsequently, laboratory experiments were conducted to perform GPR tests on different types of hard rocks in natural and water-saturated states and voids, to explore the time-frequency characteristics, frequency band energy variations, and statistical patterns of typical single-trace signals. The results show that the granite detection signal contains more low-frequency components, the sandstone detection signal contains more medium-low frequency components, while the limestone detection signal contains more medium-high frequency components in their natural state; the signal from the karst cave has relatively more low-frequency components than the signal from the empty cavity. The geometric shape of the rock has no influence on the dominant frequency and time-frequency distribution of its reflection signal. Generally, rocks with higher rebound values (hardness) also exhibit larger variance and standard deviation in frequency band energy. The research has important theoretical significance and practical value for the measurement and assessment of special geological features such as hard rocks and voids in urban underground trenchless construction.
摘要：
The attainment of formability in ceramic welding presents an imposing quandary within the realm of the manufacturing industry. In this article, the laser welding of Al2O3 ceramics was carried out to compare and analyze the influence of laser power, welding speed, laser duty cycle, and other process parameters on the macroscopic morphology of the weld, weld cracking rate, and welded joint properties. The results show that Al2O3 ceramic welds have a greater tendency to cracking and that the laser power should be matched to the appropriate welding speed. When heat input increases, the weld cracking rate decreases and then increases. Ceramic welded joints with a weld cracking rate of less than 30 % and a bending strength of more than 4 MPa can be obtained when the heat input range is 17-20.5 J/mm for continuous laser welding or 20.5-24 J/mm for pulsed laser welding. In addition, under high heat input conditions, pulsed laser welding reduces the tendency for weld cracking compared to continuous laser.
摘要：
The role of a shock generator in the fuel distribution of a scramjet engine is highly significant. In this article, the usage of the erected 3-lobe nozzle in the existence of a shock generator for fuel injection inside a supersonic combustion chamber is fully studied. A three-dimensional model of the extruded 3-lobe nozzle with two altitudes of 4 mm and 2 mm is produced to disclose the importance of the produced vortex upstream/downstream by the usage of the extruded injector. Comprehensive computational analysis is done to investigate the mixing efficiency and fuel diffusion of the proposed jet configuration. Impacts of the coaxial inward air jet on the hydrogen dispersion of the annual extruded 3-lobe injector are also revealed in the present research. The results of the flow structure indicate that the produced vortex upstream of the erected nozzle improves the fuel dispersion behind the hydrogen jet. Our findings show that the effects of injector height are more considerable than the use of an inner air jet for advance of the fuel mixing within the combustor of a scramjet engine.
期刊：
Journal of Materials Engineering and Performance,2024年 ISSN：1059-9495
通讯作者：
Jiang, BC;Jiang, Bingchun;Zhao, J
作者机构：
[Jiang, Bingchun] Guangdong Univ Sci & Technol, Dongguan, Peoples R China.;[Jiang, Bingchun; Zhao, Jun; Lu, Liwei; Liu, Yang; Zhao, J] Hunan City Univ, Yiyang, Peoples R China.;[Chai, Yanfu] Shaoxing Univ, Shaoxing, Peoples R China.
通讯机构：
[Jiang, BC; Zhao, J ] H;[Jiang, BC ] G;Guangdong Univ Sci & Technol, Dongguan, Peoples R China.;Hunan City Univ, Yiyang, Peoples R China.
关键词：
Gd and Mn alloying;Mg-Bi alloy;texture;tensile properties
摘要：
This study investigated the effect of the synergistic addition of Gd and Mn on the microstructure and mechanical properties of extruded Mg-1Bi alloys. The grain size of an Mg-1Bi alloy decreased sharply when either only Gd or Mn was added to the alloy, whereas a strong grain refining effect was verified upon the co-addition of Gd and Mn. The Mg-1Bi and Mg-1Bi-0.4Mn alloys exhibited typical strong basal textures, whereas the Mg-1Bi-0.3Gd and Mg-1Bi-0.3Gd-0.6Mn alloys showed weakened extrusion direction (ED)-split textures. The weakened ED-split texture leads to a high average Schmid factor for basal slip (SFb). Higher SFb for the sheet exhibited the lower yield strength and higher ductility. Furthermore, the synergistic addition of Gd and Mn resulted in considerably higher strength and ductility than the addition of either Gd or Mn alone. The Mg-1Bi-0.3Gd-0.6Mn sheet shows the ultimate tensile and yield strengths of similar to 275.6 and similar to 180.2 MPa along the transverse direction (TD) and similar to 273.2 and similar to 155.4 MPa along the extrusion direction (ED), respectively. Moreover, the elongation of Mg-1Bi-0.3Gd-0.6Mn sheet along the TD and ED increased to similar to 7.3 and similar to 7.5%, respectively, more than two times compared with the corresponding values for the Mg-1Bi sheet. The increased yield strength of the Mg-1Bi-0.3Gd-0.6Mn sheet was mainly attributed to the effect of refined grain size, fine alpha-Mn and MgBiGd particles, and the Gd solute. In addition, the ductility of the Mg-1Bi-0.3Gd-0.6Mn sheet was substantially increased because of the fine grain size and weak texture having a high average SFb.
