期刊:
The Journal of Organic Chemistry,2023年88(20):14697-14707 ISSN:0022-3263
通讯作者:
Chen, Shanping;Deng, GJ
作者机构:
[Quan, Siying; Fang, Fang; Xia, Jie; Chen, Shanping; Deng, Guo-Jun; Chen, SP; Deng, GJ] Xiangtan Univ, Key Lab Green Organ Synth & Applicat, Key Lab Environm Friendly Chem & Applicat, Coll Chem,Minist Educ Hunan Prov, Xiangtan 411105, Peoples R China.;[Fang, Fang] Hunan City Univ, Coll Mat & Chem Engn, Yiyang 413000, Peoples R China.;[Deng, Guo-Jun; Deng, GJ] Henan Normal Univ, Sch Chem & Chem Engn, Xinxiang 453007, Peoples R China.
通讯机构:
[Chen, SP; Deng, GJ ] X;Xiangtan Univ, Key Lab Green Organ Synth & Applicat, Key Lab Environm Friendly Chem & Applicat, Coll Chem,Minist Educ Hunan Prov, Xiangtan 411105, Peoples R China.;Henan Normal Univ, Sch Chem & Chem Engn, Xinxiang 453007, Peoples R China.
摘要:
A facile and practical approach for the preparation of substituted pyrimidines from ketones, NH4OAc, and N,N-dimethylformamide dimethyl acetal has been described. This NH4I-promoted three-component tandem reaction affords a broad range of substituted pyrimidines in acceptable yields under metal- and solvent-free conditions. The present methodology features the advantages of simple and easily available starting materials, metal- and solvent-free conditions, a broad substrate scope with good functional group tolerance, and gram-scale synthesis.
作者机构:
[Qiu, Zhenjie; Qiu, Liang; Sun, Mengying; Tang, Zhenwen] Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang, Peoples R China.;[Qiu, Zhenjie; Sun, Mengying] Hunan City Univ, Hunan Village Drinking Water Qual Safety Engn Res, Yiyang, Peoples R China.;[Hou, Xiaoli] Hunan Sany Polytech Coll, Changsha, Peoples R China.;[Hou, Xiaoli] Hunan Agr Univ, Changsha, Peoples R China.;[Qiu, Zhenjie] Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Peoples R China.
通讯机构:
[Zhenjie Qiu; Zhenjie Qiu Zhenjie Qiu Zhenjie Qiu] H;Hunan Engineering Research Center of Structural Safety and Disaster Prevention for Urban Underground Infrastructure, Hunan City University, Yiyang, China<&wdkj&>Hunan Village Drinking Water Quality Safety Engineering Research Center, Hunan City University, Yiyang, China
关键词:
emitter discharge rate;irrigation level;lateral depth;microirrigation;soil acidification;Micro-irrigation;Taux de débit de buse individuelle;Profondeur latérale;Niveau d'irrigation;Acidification du sol
摘要:
Abstract Accelerated soil acidification from excessive nitrogen fertilizer use and unreasonable irrigation has seriously increased. The advantages of saving water and fertilizer make drip irrigation feasible for reducing soil acidification. However, it is still unknown how drip irrigation influences the distribution of pH in the soil. Experiments were conducted in 30° wedge‐shaped plexiglass containers to study the transformation of nitrogen and the distribution of pH in the soil profile under subsurface drip irrigation. The apparent cylindrical water application rate varied from 4.8 to 12 L, the emitter discharge rate varied from 1.8 to 5.5 L/h, and the lateral depth ranged from 0 to 20 cm. Ten days after irrigation ended, a lateral depth of 20 cm noticeably reduced soil pH at a depth of 10–40 cm, while the pH at a shallow lateral depth decreased in the topsoil; similarly, an emitter discharge rate of 1.8 L/h significantly decreased soil pH at a depth of 0–40 cm, while the pH with a greater emitter discharge rate was slightly decreased in the topsoil. Furthermore, an increase in the application rate resulted in an increase in the area of pH decrease in the soil at 10 days after irrigation ended. Additionally, the growing nitrogen application rate significantly increased the nitrogen content in the soil profile, and the potential risk of deep‐soil pH declined. To reduce NO3‐N leaching and avoid deep‐soil acidification, a dripline depth of 10 cm with a minor irrigation level and nitrogen application rate through an emitter discharge rate of 3.2 L/h may be suggested. Résumé L'acidification accélérée des sols due à l'excès d'engrais azotés et à une irrigation déraisonnable a sérieusement augmenté. Les avantages de l'économie d'eau et d'engrais rendent l'irrigation goutte à goutte possible pour réduire l'acidification des sols. Cependant, on ne sait toujours pas comment l'irrigation goutte à goutte influence la répartition du pH dans le sol. Des expériences ont été menées dans des conteneurs en plexiglas en forme de coin à 30° pour étudier les transformations de l'azote et la répartition du pH dans le profil du sol sous irrigation souterraine goutte à goutte. Le taux d'application d'eau cylindrique apparent variait de 4,8 à 12 L, le taux de débit de buse individuelle variait de 1,8 à 5,5 L/h, et la profondeur latérale variait de 0 à 20 cm. Dix jours après la fin de l'irrigation, une profondeur latérale de 20 cm a sensiblement réduit le pH du sol à des profondeurs de 10–40 cm, tandis que le pH à une faible profondeur latérale a diminué dans la couche arable; de même, un taux de débit de buse individuelle de 1,8 L/h a significativement diminué le pH du sol à une profondeur de 0–40 cm, tandis que le pH avec un taux de débit de buse individuelle plus élevé a légèrement diminué dans la couche arable. En outre, une augmentation du taux d'application a entraîné une augmentation de la zone de diminution du pH dans le sol 10 jours après la fin de l'irrigation. En outre, le taux croissant d'application d'azote a augmenté de manière significative la teneur en azote dans le profil du sol, et le risque potentiel de pH du sol profond a diminué. Pour réduire le lessivage de NO3‐N et éviter l'acidification profonde du sol, une profondeur de 10 cm de la ligne de goutte à goutte avec un niveau d'irrigation inférieur et un taux d'application d'azote à travers un taux de débit de buse individuelle de 3,2 L/h peut être proposé.
期刊:
Journal of the Indian Society of Remote Sensing,2023年:1-16 ISSN:0255-660X
通讯作者:
Huang, CJ
作者机构:
[Xue, Yun; Huang, Changjun; Cao, Yuanzhi; Liu, Fenliang] Hunan City Univ, Sch Municipal & Surveying Engn, Yiyang 413000, Peoples R China.;[Huang, Changjun] Key Lab Key Technol Digital Urban Rural Spatial Pl, Yiyang 413000, Peoples R China.;[Zhou, Lv] Guilin Univ Technol, Sch Geomat & Geoinformat, Guilin 541004, Peoples R China.
通讯机构:
[Huang, CJ ] H;Hunan City Univ, Sch Municipal & Surveying Engn, Yiyang 413000, Peoples R China.;Key Lab Key Technol Digital Urban Rural Spatial Pl, Yiyang 413000, Peoples R China.
关键词:
Longmenshan fault zone;Wenchuan earthquake;SBAS-InSAR;Deformation characteristic;ENVISAT ASAR
摘要:
Fault activity property is one of the main reasons caused by the motion of crustal fault, and the research of fault activity characteristics has become an important direction in the study of earthquake prediction, which is an important source of new theory and new method in earthquake prediction science. The disastrous May 12, 2008, Mw7.9 Wenchuan earthquake in the Longmenshan fault zone (LFZ) took the local population as well as scientists by surprise. To analyze the temporal and spatial deformation characteristics of the Mao county-Wenchuan fault, the Beichuan-Yingxiu fault, and Jiangyou-Guan County in the central south segment of the LFZ after the Wenchuan earthquake, the SBAS-InSAR method was adopted to derive surface deformation rate with 20 Envisat SAR images acquired between August 6, 2007, and July 26, 2010. Our analysis shows that the overall movement speed of LFZ increased significantly, reaching about - 40 mm/year, which shows a dextral compression strike-slip. From west to east, the velocity changes of each section are different, and the movement of the front-range fault is dominant in the middle and south sections of Longmenshan, which is close to the epicenter. The reason may be related to the fact that the middle and south section of Longmenshan is the epicenter of the earthquake. The southern and mid-southern sections of the LFZ change from west to east, and the direction of profile movement increases gradually. In the middle and north segment of the fault zone between the two, the variation characteristics are not obvious. To a certain extent, it indicates that the fault is characterized by dextral strike-slip compression in the southern segment and the mid-southern segment. The difference in the profile movement direction in the LFZ may be related to the stress release of the southern segment of the LFZ after the earthquake while the movement of the northern segment of the LFZ was blocked. The research results will reveal the mechanism of earthquake pregnancy and earthquake generation of LFZ, enrich the knowledge of the impact on the aftershock distribution of the Wenchuan earthquake, and promote the development of earthquake prediction research.
摘要:
Low-carbon cities (LCCs) have attracted considerable attention from researchers over the past 15 years as an important initiative for mitigating global warming. The increased pilot LCCs in several countries and focus on theoretical research suggest the need to explore the associated research topics and characteristics, trends, and challenges. An in-depth analysis of literature on LCCs was conducted using the three-phase research involving documents searching, quantitative analyses and qualitative analyses. The quantitative analysis revealed that nearly 70% of LCC research was conducted in three countries. The results of the quantitative analysis also generated a map of term clusters, which identified the 9 major areas. A qualitative analysis of the literature indicated that transition to low-carbon energy is the most intensively researched category, and LCC planning and design dominates the research field. Based on the results of the quantitative and qualitative analyses, this study reports knowledge gaps in the literature and proposes future directions for LCC research in the context of four major trends: LCC planning and design, low-carbon energy transition, low-carbon decision support, and low-carbon management and policy. This study improves the existing knowledge on LCC-related research and pro-vides a future guidance for theoretical research and pilot practices related to LCC.
作者机构:
[Tang, Hui; Ao, Rongjun; Zhou, Xiaoqi; Aihemaitijiang, Yierfanjiang; Chen, Jing] Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat Hubei Prov, Wuhan, Hubei, Peoples R China.;[Tang, Hui; Ao, Rongjun; Zhou, Xiaoqi; Aihemaitijiang, Yierfanjiang; Chen, Jing] Cent China Normal Univ, Coll Urban & Environm Sci, Wuhan, Hubei, Peoples R China.;[Tang, Hui] Hunan City Univ, Sch Architecture & Urban Planning, Yiyang, Hunan, Peoples R China.
通讯机构:
[Aihemaitijiang, Y ] C;Cent China Normal Univ, Key Lab Geog Proc Anal & Simulat Hubei Prov, Wuhan, Hubei, Peoples R China.;Cent China Normal Univ, Coll Urban & Environm Sci, Wuhan, Hubei, Peoples R China.
摘要:
High-quality regional development should be promoted by facilitating inter-regional mobility of heterogeneous labor force to optimize its spatial allocation. This study incorporates skill relatedness into spatial categorization and selection effects, and explores how skill-relatedness affects the location choice of heterogeneous labor force. To do so, we use labor force migration data and employee data by occupation subcategory from the 2000 National Population Census and 2015 National Population Sample Survey. The empirical evidence provides three major findings. First, there are significant regional differences in labor migration rates by the occupational group between cities in China, and the trend is increasing. Regional concentration of location choice is increasing and six significant agglomerations are formed. Second, skill relatedness positively affects the location choice of the heterogeneous labor force in Chinese cities. When cities' skill-relatedness is more robust, influence on labor location choice is more remarkable. In cities with high-size classes, the effect of high-skill relatedness on labor location choice is higher. Third, labor force with solid skill relatedness with regional employment moves to the location owing to the spatial sorting effect. Labor force without skill relatedness or weak relatedness moves out or does not move to the location owing to the spatial selection effect.
期刊:
Journal of Manufacturing Processes,2023年101:795-806 ISSN:1526-6125
通讯作者:
Cui, JJ
作者机构:
[Li, Guangyao; Cui, JJ; Zhu, Jiapei; Cui, Junjia; Chen, Chang; Jiang, Hao; Liu, Quanxiaoxiao] Hunan Univ, State Key Lab Adv Design & Mfg Technol Vehicle, Changsha 410082, Peoples R China.;[Chen, Chang] Hunan City Univ, Sch Mech & Elect Engn, Yiyang 413000, Peoples R China.;[Li, Guangyao] Beijing Inst Technol, Shenzhen Automot Res Inst, Shenzhen Res Inst, Natl Engn Lab Elect Vehicles, Shenzhen 518118, Peoples R China.
通讯机构:
[Cui, JJ ] H;Hunan Univ, State Key Lab Adv Design & Mfg Technol Vehicle, Changsha 410082, Peoples R China.
关键词:
Magnetic pulse spot welding;Aluminium alloy sheet;Mechanical property;Micro-morphology
摘要:
Magnetic pulse spot welding (MPSW) is a safe, efficient and environmentally friendly process, which is very suitable for joining aluminium alloys. AA5052 aluminium alloy sheets were joined by MPSW. Specifically, the bump on the flyer plate was driven to impact the parent plate at high velocity to achieve metallurgical bonding. The formation process, mechanical properties and micro-morphology of the joint were studied. The results showed that the bump of the flyer plate impacted the parent plate at high velocity caused by Lorentz force to form welding seam. The shape of the welding seam was two incompletely continuous symmetrical elliptical arcs due to the different welding velocities and welding angles in each zone. The strength of the joint was higher than that of the base metal at appropriate process parameters. Specifically, the relatively better process parameters were welding gap of 1.4 mm, welding diameter of 16 mm and discharge energy of 36 kJ. The maximum loads of tensile shear and cross-tension were 4887 N, 1744 N. There were a large amount of dimples at the fracture of welding seam, and the toughness of joint was good.
作者机构:
[Ge, Yaping; Tang, Huang; Yang, Yiming; Li, Hai] Hunan City Univ, Hunan Engn Res Ctr Dev & Applicat Ceramsite Concre, Yiyang 413000, Peoples R China.;[Tang, Huang] Changsha Univ Sci &Technol, Key Lab Safety Control Bridge Engn Minist Educ, Changsha 410114, Peoples R China.;[Xiao, Linfa] East China Jiaotong Univ, Sch Transportat Engn, Nanchang 330013, Jiangxi, Peoples R China.
通讯机构:
[Yang, YM ] H;Hunan City Univ, Hunan Engn Res Ctr Dev & Applicat Ceramsite Concre, Yiyang 413000, Peoples R China.
关键词:
Chloride salt erosion;Freeze-thaw cycle;Interface shear strength;Self-compacting concrete
摘要:
Self-compacting concrete (SCC) has been widely used for concrete jacketing to strengthen RC structures due to its high workability, fluidity, and segregation resistance. In this study, a test was carried out to study the effects of substrate curing including chloride salt erosion and the freeze–thaw cycle on the interface shear strength between ordinary concrete and the SCC. Eighty-four Z-type specimens were designed and tested through direct shear experiments, and the influence of interface treatment (implanting steel bar and cutting groove), concrete type, and substrate curing on the interface shear strength were analyzed. Four calculation models of interface shear strength based on different codes are compared, the applicability of these models is also analyzed. The results show that: For close the substrate concrete and the SCC strength, the effect of chloride salt erosion and freeze–thaw cycle will cause a slight decrease in the interface shear strength compared with the specimen that substrate is not cured, the influence of chloride ion erosion and freeze–thaw cycle on the degeneration of interface shear strength for specimen with implanting steel bar is not more obviously than specimen with cutting groove. Any single code model can not accurately predict the interface shear strength of all specimens with different interface treatments and substrate curing. The fib model can accurately predict interface shear strength of specimens which the average compressive strength of old and new concrete is less than 40 MPa and the substrate is not cured. Whether the substrate is cured or not, EC2 and CSA A23.3–14 models can quite accurately predict the interface shear strength of specimens with an implanting steel bar, but for specimens with cutting groove, the modified AASHTO model can accurately predict the interface shear strength. Except modified AASHTO model, the factor considering the effect of interface treatment should be taken into account when using fib, EC2 and CSA A23.3–14 models to calculate the interface shear strength.
摘要:
Though building-scale energy demand and indoor thermal comfort have been extensively covered by recent studies, the automation of middle- and larger-scale outdoor microclimate evaluation in parametric design is less covered. The relatively slow computation and the need for sophisticated expertise are some of the current issues. This paper proposes a Rhino–Grasshopper custom script to automatically compute spatial indicators for a quick thermal comfort estimation. The Galapagos evolutionary algorithm is used to optimize thermal comfort and select the best combinations of spatial indicators. In a summer case study located in Shantou, China, the proposed workflow was three times faster than a non-automated indicator calculation in ArcGIS, while the optimization method achieved 25% to 33% reduction in land areas under extreme heat stress. This automated process applies to existing states and new urban designs. It is adaptable to customized prediction models under different climatic zones.
摘要:
Sulfur dioxide (SO(2)) derivatives are extensively utilized as both a preservative for foods and an active gaseous signal molecule in various physiological and pathological processes, but their excessive intake would bring harmful effects on human health; so, the determination of SO(2) derivatives is of great importance. Herein, we developed a ratiometric fluorescent probe named 2-(2'-hydroxyphenyl)benzothiazole-3-ethyl-1,1,2-trimethyl-1H-benzo[e]indolium (HBT-EMBI) by introducing a hemicyanine unit of EMBI to an HBT group for the detection of SO(2) derivatives via an excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT) effects. The probe displays some advantages, such as a colorimetric change from purple to colorless, a ratiometric fluorescence with zero cross-talk, and a remarkably large emission shift (Δλ = 164 nm) under a single-wavelength excitation. Accordingly, the probe HBT-EMBI has been successfully employed for the colorimetric and ratiometric determination of SO(2) derivatives in real food samples and the quantitative visualization of SO(2) derivative variations in HepG2 cells.
摘要:
BiCuSeO compound is a promising thermoelectric material, which has attracted many experimental stud-ies through trial-and-error approaches to improve its thermoelectric performance by element doping, such that a fast and efficient prediction of thermoelectric property for unexplored and rarely explored doped-BiCuSeO is highly desired. In this work, a machine learning (ML) model for predicting the ZT value of M element doped-BiCuSeO (Bi1-xMxCuSeO) has been established via the correlation analysis for descriptors and the comparison among different ML approaches. The results show that Gradient Boosting Regressor is the most appropriate approach for our ML model, which is well validated by com-paring the predicted and experimental ZT values for the cases in the dataset. The ML model is also used to predict the ZT values of Bi1-xMxCuSeO with unexplored and rarely explored doping element M, and the optimal doping elements as well as their doping contents are screened out. The results indicate that the ZT of Bi0.86Po0.14CuSeO (Po-doped) and Bi0.88Cs0.12CuSeO (Cs-doped) are higher than that of pure BiCuSeO, and are improved by 104 % and 98 % at the 923 K, respectively. The enhancement is well explained by the first-principles calculations. The findings offer a guideline for exploring superior ther-moelectric performance in BiCuSeO.(c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
摘要:
In recent years, the provision of applications based on conferencing services over Software-Defined Networking (SDN) is increasing. So far, extensive studies have been conducted on improving conferencing services and supporting high-quality communication in SDN, and the importance of the issue has been understood by the research society. One of the challenges of guaranteeing conferencing services in SDN is the routing of network traffic taking into account Quality of Service (QoS) requirements. Most routing techniques in SDN guarantee end-to-end delay and bandwidth constraints. However, resource loss also plays a role in network performance, where it is clearly neglected in existing works. This study presents a guaranteed Latency-Bandwidth-Loss Routing algorithm based on Fuzzy approach to improve the performance of conference services in SDN (LBLRF). The purpose of the fuzzy-based approach is to increase the number of routed requests and improve the performance of conference services in SDN. LBLRF uses a postponement mechanism to improve the conference service, where it gives higher priority to the requests with low resource demand for connection. In addition, LBLRF is equipped with a hold time mechanism to release the reserved resources after satisfying the request requirements. This mechanism can increase the processing capacity of future requests by conserving network resources. Evaluations have been done by defining several scenarios on a synthetic SDN environment. The results of the experiments show that LBLRF provides a better request acceptance rate between 7% and 16% compared to the best results of existing algorithms.
摘要:
Most plants belonging to the widely distributed genus Dianthus are used for gardening. Interspecific hybridization of different Dianthus species leads to blurred genetic backgrounds. To obtain more genomic resources and understand the phylogenetic relationships among Dianthus species, the chloroplast genomes of 12 Dianthus species, including nine Dianthus gratianopolitanus varieties, were analyzed. The chloroplast genomes of these 12 species exhibited similar sizes (149,474-149,735 bp), with Dianthus caryophyllus having a chloroplast genome size of 149,604 bp marked by a significant contraction in inverted repeats. In the chloroplast genome of Dianthus, we identified 124-126 annotated genes, including 83-84 protein-coding genes. Notably, D. caryophyllus had 83 protein-coding genes but lacked rpl2. The repeat sequences of the chloroplast genome were consistent among species, and variations in the sequence were limited and not prominent. However, notable gene replacements were observed in the boundary region. Phylogenetic analysis of Dianthus indicated that D. caryophyllus and D. gratianopolitanus were most closely related, suggesting that the degree of variation within nine Dianthus varieties was no less than the variation observed between species. These differences provide a theoretical foundation for a more comprehensive understanding of the diversity within Dianthus species.
期刊:
Sustainable Energy Technologies and Assessments,2023年57:103230 ISSN:2213-1388
通讯作者:
Mohamed Salem
作者机构:
[Peng, Li] Key Laboratory for Energy Monitoring and Edge Computing of Smart City, Hunan City University, Yiyang 413002, China;[Salem, Mohamed] School of Electrical and Electronic Engineering, Universiti Sains Malaysia (USM), Nibong Tebal, 14300 Penang, Malaysia;[Blazek, Vojtech; Prokop, Lukas; Misak, Stanislav] ENET Centre, VSB—Technical University of Ostrava, 708 00 Ostrava, Czech Republic;[Al-Bahrani, Mohammed] Chemical Engineering and Petroleum Industries Department, Al-Mustaqbal University College, Babylon 51001, Iraq
通讯机构:
[Mohamed Salem] S;School of Electrical and Electronic Engineering, Universiti Sains Malaysia (USM), Nibong Tebal, 14300 Penang, Malaysia
关键词:
Solar water heaters;Renewable energy;Buildings;Thermal energy storage;Phase change material (PCM)
摘要:
Fossil fuel usage for heating applications must be reduced considering the issues related to the environment and the restriction of their resources. In this regard, attention is devoted to renewable energy sources to supply the energy requirements of different sectors. In the building sector, solar energy is harnessed for heating and cooling. Solar energy is applicable both directly and indirectly for heating using different technologies. The intermittent nature of solar energy obliges the use of storage units to make the solar systems applicable at night hours or during periods the low solar intensity. Various thermal energy storage materials have been utilized in different kinds of solar heaters to stabilize their performance, improve their reliability, and avoid issues related to variations in solar radiation. In this article, studies on the usage of thermal energy storage units in solar water heaters are reviewed and their key results are reflected. As one of the main conclusions of the reviewed works, it can be denoted that several factors such as the operation condition and characteristics of the storage unit are effective on the function of the systems combined with the thermal storage component. Aside from an increment in the operating hours of solar heaters, usage of storage units can boost both energy and exergy efficiencies. Furthermore, the study denotes that the power saving rate is influenced by the abundance of solar energy resources. In addition, it could be denoted that the performance of the systems is improvable by employing some ideas, such as the application of nanotechnology in storage materials.
作者机构:
[Peng, Zhigao; Peng, ZG; Feng, Haoxiong; Xiao, Ming] Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;[Peng, Zhigao; Peng, ZG] Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Hunan, Peoples R China.;[Liu, Shenggui] Univ Min & Technol Beijing, Sch Mech & Civil Engn, Beijing 100083, Peoples R China.;[Long, Yanqing] Hunan Tunnel Engn Co LTD, Yiyang 413000, Peoples R China.
通讯机构:
[Peng, ZG ] H;Hunan City Univ, Coll Civil Engn, Yiyang 413000, Peoples R China.;Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Hunan, Peoples R China.
摘要:
The occurrence of coalbed methane adsorption-desorption hysteresis has been widely observed, but a unified understanding of its mechanism is lacking, and the factors affecting its degree are unclear. This study introduces a microscale LB model for gas diffusion-adsorption-desorption in porous media that also accounts for the adsorption-desorption hysteresis effect. The accuracy of the model has been validated using previous experimental data, and the primary controlling factors of adsorption-desorption hysteresis were analyzed. The findings are as follows: (1) In the process of methane diffusion-adsorption-desorption, Knudsen diffusion dominates in micro- and mesopores, while viscous flow prevails in macropores; our model can adaptively adjust gas transport regimes across a broad range of pore sizes and pressures. (2) The desorption amount and rate are close relative to the correction factors α and β. A higher α value corresponds to greater initial adsorption as well as longer desorption time, whereas a lower β value implies weaker desorption capacity and a slower desorption rate. (3) Pore size can affect gas diffusion-adsorption-desorption kinetics, where larger pore size corresponds to efficient gas diffusivity; when r < 10 nm, the desorption process is mainly controlled by the desorption rate. Overall, this study has offered new insights into the mechanism behind methane adsorption-desorption hysteresis at the microscale, identified primary controlling factors of methane diffusion-adsorption-desorption process, and provided a foundation for numerical simulations and experiments related to the adsorption-desorption hysteresis.
关键词:
Viscoelastic fluid;Activation energy;Stagnation point flow;Heat generation/absorption;Generalized Fourier and Fick ' s law;Stretching sheet
摘要:
This analysis describes the stagnation point and mixed convection flow of a viscoelastic micropolar fluid into a porous medium towards a stretchable sheet and magnetic field. Concentration and thermal stratification boundary conditions and activation energy are studied. For the flow of heat and mass transportation, Fourier and Fick's law is also accommodated into account. Suitable similarity variables are utilized to attain the dimen-sionless form of the governed equations. These dimensionless equations have been resolved numerically with the help of BVP4C approach. The velocity profile is reduced with the stronger estimations of eand M. The coefficient of skin friction has an increasing effect by improving values of K, fi, M, and SMALL ELEMENT OF. The velocity sketch has the opposite behavior for SMALL ELEMENT OF and fit. Stronger estimations of fi and Se lead to the decay of the temperature profile. The angular velocity of the fluid upsurges due to the stronger values of K.
摘要:
Through gravity/gauge duality, the string breaking and running coupling constant of heavy quarkantiquark pair are investigated in the rotating background. For the meson decay mode QQ -> Qq + Qq, we discuss the string breaking and running coupling in the parallel and transverse case. It is found that the parallel case has a more significant on string breaking and running coupling constant than the transverse case in the confined phase. The string-breaking distance and the maximum value of running coupling will decrease with the increase of angular velocity in the parallel case. Besides, we also investigate the running coupling and screening distance at finite angular velocity in the deconfined phase. It is found that the maximum values of the running coupling and screening distance are decreasing functions of angular velocity. The parallel case has a more significant influence on the running coupling and screening distance than the transverse case in the deconfined phase. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3.
摘要:
Fuel cells are a newly developed source for generating electric energy. These cells produce electricity through a chemical reaction between oxygen and hydrogen, which releases electrons. In recent years, extensive research has been conducted in this field, leading to the emergence of high-power batteries. This study introduces a novel technique to enhance the power quality of grid-connected proton-exchange membrane (PEM) fuel cells. The proposed approach uses an inverter following a buck converter that reduces voltage. A modified pelican optimization (MPO) algorithm optimizes the controller firing. A comparison is made between the controller’s performance, based on the recommended MPO algorithm and various other recent approaches, demonstrating the superior efficiency of the MPO algorithm. The study’s findings indicate that the current–voltage relationship in proton-exchange membrane fuel cells (PEMFCs) follows a logarithmic pattern, but becomes linear in the presence of ohmic overvoltage. Furthermore, the PEMFC operates at an impressive efficiency of 60.43% when running at 8 A, and it can deliver a significant power output under specific operating conditions. The MPO algorithm surpasses other strategies in terms of efficiency and reduction in voltage deviation, highlighting its effectiveness in managing the voltage stability, and improving the overall performance. Even during a 0.2 sagging event, the MPO-based controller successfully maintains the fuel cell voltage near its rated value, showcasing the robustness of the optimized regulators. The suggested MPO algorithm also achieves a superior accuracy in maintaining the voltage stability across various operating conditions.
期刊:
Physical Chemistry Chemical Physics,2023年25(25):17034-17042 ISSN:1463-9076
通讯作者:
Xiong, CX
作者机构:
[Xiong, Cuixiu; Zhang, Saiwen; Tan, Meng; Wan, Can; Wei, Chengya; Wang, Jie; Xiong, CX] Hunan City Univ, Coll Informat & Elect Engn, All Solid State Energy Storage Mat & Devices Key L, Yiyang 413000, Peoples R China.
通讯机构:
[Xiong, CX ] H;Hunan City Univ, Coll Informat & Elect Engn, All Solid State Energy Storage Mat & Devices Key L, Yiyang 413000, Peoples R China.
摘要:
A fully continuous geometric center symmetric cross-shaped graphene structure is proposed. Each cross-shaped graphene unit cell is composed of a central graphene region and four completely symmetric graphene chips, where each graphene chip acts as both bright and dark modes simultaneously, while the central graphene region always acts as the bright mode. Through destructive interference, the structure can realize the single plasmon-induced transparency (PIT) phenomenon, where the optical responses are independent of the polarization direction of the linearly polarized light due to the symmetry of the structure. Combining numerical simulations with coupled mode theory (CMT) calculations, the modulation of the Fermi energy of graphene to the optical spectra is investigated. The results show that the spectra are blue shifted as the Fermi energy increases, and the absorption of the two absorption peaks is basically equal (48.7%) when the Fermi energy increases to 0.667 eV. Theoretical calculations show that the slow light performance of the designed structure enhances with the increase of Fermi energy, where the maximum group index is high up to 424.73. Furthermore, it is worth noting that the electrode can be made very small due to its fully continuous structure. This work provides guidance in terms of terahertz modulators, tunable absorbers, and slow light devices.
期刊:
Structural Control and Health Monitoring,2023年2023 ISSN:1545-2255
通讯作者:
Hu, D
作者机构:
[Yang, Xian; Liang, Xiaoqiang; Hu, Da; Li, Yongsuo; Hu, D] Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Peoples R China.;[Hu, Da; Hu, D] Power China Zhongnan Engn Co Ltd, Hunan Prov Key Lab Key Technol Hydropower Dev, Changsha 410014, Peoples R China.;[Zhang, Keneng] Cent South Univ, Key Lab Metallogen Predict Nonferrous Met & Geol E, Minist Educ, Changsha 410083, Peoples R China.;[Liang, Xiaodong] Hunan Lianzhi Technol Co Ltd, Changsha 410100, Peoples R China.
通讯机构:
[Hu, D ] H;Hunan City Univ, Hunan Engn Res Ctr Struct Safety & Disaster Preven, Yiyang 413000, Peoples R China.;Power China Zhongnan Engn Co Ltd, Hunan Prov Key Lab Key Technol Hydropower Dev, Changsha 410014, Peoples R China.
摘要:
In recent years, 3D laser scanning technology has been applied to tunnel engineering. Although more intelligent than traditional measurement technology, it is still challenging to estimate the real-time deformation of NATM tunnel excavation from laser detection and ranging point clouds. To further improve the measurement accuracy of 3D laser scanning technology in the tunnel construction process, this paper proposes an improved Kriging filtering algorithm. Considering the spatial correlation of the described object, the optimization method of point cloud grid filtering is studied. By analyzing the full-space deformation field of the tunnel lining, the deformation information of the measuring points on the surface of the tunnel lining is extracted. Based on the actual project, through the on-site monitoring comparison test, the three-dimensional laser point cloud data are grid processed and analyzed, and the deformation data obtained from the test are compared with the data measured by traditional methods. The experimental results show that the Kriging filtering algorithm can not only efficiently identify and extract the tunnel profile visualization data but also efficiently and accurately obtain the tunnel deformation. The measurement results obtained by using the proposed technology are in good agreement with those obtained by using traditional monitoring methods. Therefore, tunnel deformation monitoring based on 3D laser scanning technology can better reflect the evolution of the tunnel full-space deformation field under certain environmental conditions and can provide an effective safety warning for tunnel construction.