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An Improved Solov2 Based on Attention Mechanism and Weighted Loss Function for Electrical Equipment Instance Segmentation
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作者 Junpeng Wu Zhenpeng Liu +2 位作者 Xingfan Jiang Xinguang Tao Ye Zhang 《Computers, Materials & Continua》 SCIE EI 2024年第1期677-694,共18页
The current existing problem of deep learning framework for the detection and segmentation of electrical equipment is dominantly related to low precision.Because of the reliable,safe and easy-to-operate technology pro... The current existing problem of deep learning framework for the detection and segmentation of electrical equipment is dominantly related to low precision.Because of the reliable,safe and easy-to-operate technology provided by deep learning-based video surveillance for unmanned inspection of electrical equipment,this paper uses the bottleneck attention module(BAM)attention mechanism to improve the Solov2 model and proposes a new electrical equipment segmentation mode.Firstly,the BAM attention mechanism is integrated into the feature extraction network to adaptively learn the correlation between feature channels,thereby improving the expression ability of the feature map;secondly,the weighted sum of CrossEntropy Loss and Dice loss is designed as the mask loss to improve the segmentation accuracy and robustness of the model;finally,the non-maximal suppression(NMS)algorithm to better handle the overlap problem in instance segmentation.Experimental results show that the proposed method achieves an average segmentation accuracy of mAP of 80.4% on three types of electrical equipment datasets,including transformers,insulators and voltage transformers,which improve the detection accuracy by more than 5.7% compared with the original Solov2 model.The segmentation model proposed can provide a focusing technical means for the intelligent management of power systems. 展开更多
关键词 Deep learning electrical equipment attention mechanism weighted loss function
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Losses of Soil Organic Carbon and Nitrogen and Their Mechanisms in the Desertification Process of Sandy Farmlands inHorqin Sandy Land 被引量:3
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作者 SU Yong-zhong and ZHAO Ha-lin(Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences,Lanzhou 730000 , P. R. China) 《Agricultural Sciences in China》 CAS CSCD 2003年第8期890-897,共8页
Soil organic carbon(SOC)and total nitrogen(N)concentrations from bulk soils and soil particle size fractions in the different extent of desertified farmlands(potential, light, medium, severe, and most severe desertifi... Soil organic carbon(SOC)and total nitrogen(N)concentrations from bulk soils and soil particle size fractions in the different extent of desertified farmlands(potential, light, medium, severe, and most severe desertified farmlands)were examined to quantitatively elucidate losses of carbon and nitrogen and its mechanisms in the desertification process. Particle size fractions(2 -0.1 mm, 0.1 - 0.05 mm, <0.05 mm)were obtained by granulometric wet sieving from 30 sandy soils(0 - 15cm depth)of different desertified extent. It was shown that soil physical stability index(St)in most severe desertified farmlands was 5 -7% and St in other farmlands was less than 5 %, which contributed to very low soil organic matter content. This was the intrinsic cause that sandy farmlands in Horqin sandy land was subject to risk of desertification. Desertification resulted in considerable losses of SOC and N. Regression analysis indicated that SOC and N content reduced 0.169 g kg-1 and 0.0215 g kg-1 respectively with one percent loss of soil silt and clay content. Losses of SOC and N were mostly the removal of fine particle size fractions(silt and clay, and a less extent very fine sand)from the farmlands by wind erosion, which were rich in organic matter and nutrients, as well as the depletion of organic C and N associated with coarse particles(>0. 05 mm)in desertification process. The concentrations of C and N associated with sand(2 - 0.1 mm and 0.1 - 0.05 mm)significantly decreased with increase of desertified extent. Silt and clay associated C and N concentrations, however, were less changed, and in contrast, were higher in soils under most severe desertified extent than in soils under potential and severe desertified extent. The percentage of distribution in sand(>0.05 mm)associated C and N significantly increased with increase of desertified extent, suggesting that stability of SOC decreased in the desertification process. 展开更多
关键词 Farmland desertification Soil organic carbon Total nitrogen mechanisms of losses
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Loss and damage related to climate change:connotations and response mechanism 被引量:1
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作者 Xin Ma Yue Li +3 位作者 Xiaojia He Wentao Wang Shuo Liu Qinzhu Gao 《Chinese Journal of Population,Resources and Environment》 2015年第1期55-60,共6页
Global mitigative and adaptive efforts have not been able to effectively address the adverse impacts caused by climate change.Therefore,a direct solution is needed to address the significant resulting loss and damage(... Global mitigative and adaptive efforts have not been able to effectively address the adverse impacts caused by climate change.Therefore,a direct solution is needed to address the significant resulting loss and damage(L&D).During the United Nations Framework Convention on Climate Change held in Doha in 2012,the issue of responding to L&D arising from climate change gained sudden traction and became one of the key issues that affected the outcome of the convention.In this paper,a study on the definition and connotations of L&D arising from climate change was conducted,together with an analysis of its relationship with related concepts,namely impacts,vulnerability,and risks.This led to the proposal of an L&D conceptual model that is more comprehensive,with the recognition of the need to address the issue through effective supplementation of existing mitigative and adaptive efforts.A systematic elaboration of an L&D response mechanism was made based on politics,law,and the market,leading to a preliminary presentation of a possible format for an L&D mechanism.Potential academic research directions for L&D were also proposed that could serve as references for the establishment of international and national L&D response mechanisms and related research. 展开更多
关键词 CLIMATE CHANGE loss and DAMAGE connotations response mechanism
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Mechanism of Strength Loss of No-bake Phosphate Bonded Sand Mold/Core 被引量:1
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作者 张友寿 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2009年第1期5-8,共4页
The strength loss mechanism of the phosphate bonded sand mold/core was studied. The morphology and composition of phosphate membrane on the surface of sands was analyzed with electron probe X-ray microanalyzer. Result... The strength loss mechanism of the phosphate bonded sand mold/core was studied. The morphology and composition of phosphate membrane on the surface of sands was analyzed with electron probe X-ray microanalyzer. Results show that magnesium causes cracks in cured phosphate membrane and results in the decrease of sand molds/cores strength. However, the addition of magne-sium significantly enhanced hygroscopy resistance of phosphate membrane. In addition, the phosphate binder added with the magnesium modifier has more rapid hardening reaction speed compared that without or with low magnesium binder. It can be concluded that the phosphate binder with the addition of magnesium modifier is favorably used in high humid and cold circumstance. 展开更多
关键词 PHOSPHATE mechanism of strength loss CRACK hygroscopy resistance
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Precision loss of ball screw mechanism under sliding-rolling mixed motion behavior
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作者 QI Bao-bao CHENG Qiang +2 位作者 LI Shun-lei LIU Zhi-feng YANG Cong-bin 《Journal of Central South University》 SCIE EI CAS CSCD 2021年第5期1357-1376,共20页
The sliding-rolling mixed motion behavior degrades the ball screw’s precision at different levels.Based on the sliding-rolling mixed motion between ball and screw/nut raceway,the ball screw’s precision loss consider... The sliding-rolling mixed motion behavior degrades the ball screw’s precision at different levels.Based on the sliding-rolling mixed motion between ball and screw/nut raceway,the ball screw’s precision loss considering different given axial loading and rotational speed working conditions was investigated.Since creep and lubrication relate to sliding and rolling motion wear,the creep and lubrication characteristics are analyzed under different working conditions.Besides,the precision loss was calculated considering the sole influence of sliding behavior between ball and screw and compared with the results from other current models.Finally,research on precision loss owing to the sliding-rolling mixed motion behavior was realized under given working conditions,and suitable wear tests were carried out.The analytical results of precision loss are in good agreement with the experimental test conclusions,which is conducive to better predicting the law of precision loss in stable wear period. 展开更多
关键词 ball screw mechanism precision loss sliding-rolling mixed motion creep lubrication
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Biochemical Genetic Mechanism and QTLs of Early Maturing without Yield Loss in Short-season Upland Cotton(Gossypium hirsutum L.)
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作者 SONG Mei-zhen,YU Shu-xun,FAN Shu-li(Cotton Research Institute,Chinese Academy of Agricultural Sciences Key Laboratory of Cotton Genetic Improvement,Ministry of Agriculture,Anyang,Henan 455000,China) 《棉花学报》 CSCD 北大核心 2008年第S1期68-,共1页
The short season cotton(SSC) was important Upland plant ecotype(Gossypium hirsutum L.).The growth of SSC was very short that is 105 ~ 110 days(after planting). SSC could increase
关键词 QTLS Biochemical Genetic mechanism and QTLs of Early Maturing without Yield loss in Short-season Upland Cotton Gossypium hirsutum L
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Effects of Planting Density on Yield and Mechanical Harvesting Loss Rate of Brassica napus L. 被引量:8
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作者 浦惠明 胡茂龙 +1 位作者 龙卫华 高建芹 《Agricultural Science & Technology》 CAS 2015年第1期40-46,共7页
[Objective] This study aimed to explore agronomical measures to reduce the mechanical harvesting loss of rapeseed. [Method] Two rapeseed cultivars, Ningza 19 and Ningza 21, with certain pod-cracking resistance, were e... [Objective] This study aimed to explore agronomical measures to reduce the mechanical harvesting loss of rapeseed. [Method] Two rapeseed cultivars, Ningza 19 and Ningza 21, with certain pod-cracking resistance, were employed in field experiments. The two-factor split plot design and randomized complete block design were adopted. The rapeseed seeds were directly sowed with four different seeding rates (1.50, 2.25, 3.00 and 3.75 kg/hm2). A total of four treatments were designed (112 500, 225 000, 337 500 and 450 000 plants/hm2). After ripe, the rapeseed was harvested with harvester. Then the yield and harvesting loss rate were determined. [Result] When the planting density ranged from 112 500 to 450 000 plants/hm2, the mechanical harvesting loss rate was decreased with the increase of planting density (Ningza 19, 7.54%-4.01%; Ningza 21, 7.19%-3.81%). The total loss rates were all below 5% for the high plant densities, 337 500 and 450 000 plants/hm2. High planting density had certain regulating effects on plant type of rapeseed, including reducing plant height, reducing biomass per plant, reducing branch pod numbers per plant, weakening crossing and tangling among stems and improving ripening uniformity of pods. All the changes above were all conducive to reducing mechanical harvesting loss. In addition, the test results showed after the pods grew to maturity, especially when pods were yellow and the moisture content in grains was reduced to 11%, the mechanical harvesting loss only accounted for about 1% of the total field loss. In addition, the shattering loss, caused by mild col- lision, represented more than 90%, and the cleaning loss, occurred during the threshing and cleaning process, represented 4%-8% of the total field loss. The un- harvesting loss accounted for approximately 1% of the total loss. The shattering loss is closely related to cultivar characteristics, planting density, production level and other agronomic factors. The cleaning loss is determined by properties of harvesting machines. The unharvesting loss depends on mechanical properties ad skills of workers or farmers who drive harvesting machines. [Conclusion] In order to reduce mechanical harvesting loss, the rapeseed production should be improved from the perspectives of agricultural machinery and agronomic measures. 展开更多
关键词 CROPS HARVEST loss RAPESEED mechanical harvesting Planting density
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Heavy soil drying during mid-to-late grain filling stage of the main crop to reduce yield loss of the ratoon crop in a mechanized rice ratooning system 被引量:6
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作者 Chang Zheng Yuechao Wang +4 位作者 Shen Yuan Sen Xiao Yating Sun Jianliang Huang Shaobing Peng 《The Crop Journal》 SCIE CSCD 2022年第1期280-285,共6页
Yield loss(Y_(Loss)) in the ratoon crop due to crushing damage to left stubble from mechanical harvesting of the main crop is a constraint for wide adoption of mechanized rice ratooning technology.Soil drying before t... Yield loss(Y_(Loss)) in the ratoon crop due to crushing damage to left stubble from mechanical harvesting of the main crop is a constraint for wide adoption of mechanized rice ratooning technology.Soil drying before the harvest of the main crop has been proposed to overcome this problem.The objective of this study was to determine the effect of soil drying during the mid-to-late grain filling stage of the main crop on grain yield of the ratoon crop in a mechanized rice ratooning system.Field experiments were conducted to compare Y_(Loss) between light(LD) and heavy(HD) soil drying treatments in Hubei province,central China in 2017 and 2018.Y_(Loss) was calculated as the percentage of yield reduction in the ratoon crop with the main crop harvested mechanically,relative to the grain yield of the ratoon crop with the main crop harvested manually.In comparison with LD,soil hardness was increased by 42.8%-84.7% in HD at the 5-20 cm soil depth at maturity of the main crop.Soil hardness at 5 and 10 cm depths reached respectively 4.05 and 7.07 kg cm^(-2) in HD.Soil drying treatment did not significantly affect the grain yield of the main crop.Under mechanical harvesting of the main crop,HD increased the grain yield of the ratoon crop by 9.4% relative to LD.Consequently,Y_(Loss) was only 3.4% in HD,in contrast to 16.3% in LD.The differences in grain yield and Y_(Loos) between the two soil drying treatments were explained mainly by panicles m^(-2),which was increased significantly by HD in the track zone of the ratoon crop compared with LD.These results suggest that heavy soil drying practice during the mid-to-late grain filling stage of the main crop is effective for reducing Y_(Loss) of the ratoon crop in a mechanized rice ratooning system. 展开更多
关键词 Crushing damage mechanical harvesting Ratoon rice Soil drying Yield loss
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An Equivalent Substitute Strategy for Constructing 3D Ordered Porous Carbon Foams and Their Electromagnetic Attenuation Mechanism 被引量:7
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作者 Meng Zhang Hailong Ling +11 位作者 Ting Wang Yingjing Jiang Guanying Song Wen Zhao Laibin Zhao Tingting Cheng Yuxin Xie Yuying Guo Wenxin Zhao Liying Yuan Alan Meng Zhenjiang Li 《Nano-Micro Letters》 SCIE EI CAS CSCD 2022年第10期15-35,共21页
Three-dimensional(3D)ordered porous carbon is generally believed to be a promising electromagnetic wave(EMW)absorbing material.However,most research works targeted performance improvement of 3D ordered porous carbon,a... Three-dimensional(3D)ordered porous carbon is generally believed to be a promising electromagnetic wave(EMW)absorbing material.However,most research works targeted performance improvement of 3D ordered porous carbon,and the specific attenuation mechanism is still ambiguous.Therefore,in this work,a novel ultra-light egg-derived porous carbon foam(EDCF)structure has been successfully constructed by a simple carbonization combined with the silica microsphere template-etching process.Based on an equivalent substitute strategy,the influence of pore volume and specific surface area on the electromagnetic parameters and EMW absorption properties of the EDCF products was confirmed respectively by adjusting the addition content and diameter of silica microspheres.As a primary attenuation mode,the dielectric loss originates from the comprehensive effect of conduction loss and polarization loss in S-band and C band,and the value is dominated by polarization loss in X band and Ku band,which is obviously greater than that of conduction loss.Furthermore,in all samples,the largest effective absorption bandwidth of EDCF-3 is 7.12 GHz under the thickness of 2.13 mm with the filling content of approximately 5 wt%,covering the whole Ku band.Meanwhile,the EDCF-7 sample with optimized pore volume and specific surface area achieves minimum reflection loss(RL_(min))of−58.08 dB at 16.86 GHz while the thickness is 1.27 mm.The outstanding research results not only provide a novel insight into enhancement of EMW absorption properties but also clarify the dominant dissipation mechanism for the porous carbon-based absorber from the perspective of objective experiments. 展开更多
关键词 Porous carbon foam Electromagnetic wave absorption Adjustable pore structure Polarization loss Attenuation mechanism
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Urinary stone disease and obesity: Different pathologies sharing common biochemical mechanisms 被引量:2
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作者 Ozgu Aydogdu 《World Journal of Nephrology》 2012年第1期12-15,共4页
The prevalence of urolithiasis is increasing in parallel with the escalating rate of obesity worldwide. It has previously been speculated that obesity is a potential risk factor for urinary stone disease. The possibil... The prevalence of urolithiasis is increasing in parallel with the escalating rate of obesity worldwide. It has previously been speculated that obesity is a potential risk factor for urinary stone disease. The possibility that common biochemical mechanisms underlie both obesity and urolithiasis is remarkable. Better understanding of possible common mechanisms of these diseases could potentially lead to a better management of urinary stone prevention. The prevention of urinary stone for-mation gives clinicians an acceptable reason to encour-age lifestyle modification and weight loss through a regular diet. In this review, the association of obesity with urinary stone disease, possible common biochemi-cal mechanisms, effects of dietary habits and weight loss on stone formation, as well as diffculties in surgi-cal management of obese individuals with urolithiasis are discussed. 展开更多
关键词 Urinary stone disease OBESITY Biochemical mechanism Weight loss Body mass index
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Loss Factors and their Effect on Resonance Peaks in Mechanical Systems 被引量:1
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作者 Roman Vinokur 《Sound & Vibration》 EI 2023年第1期1-13,共13页
The loss factors and their effects on the magnitude and frequency of resonance peaks in various mechanical sys-tems are reviewed for acoustic,vibration,and vibration fatigue applications.The main trends and relationsh... The loss factors and their effects on the magnitude and frequency of resonance peaks in various mechanical sys-tems are reviewed for acoustic,vibration,and vibration fatigue applications.The main trends and relationships were obtained for linear mechanical models with hysteresis damping.The well-known features(complex module of elasticity,total loss factor,etc.)are clarified for practical engineers and students,and new results are presented(in particular,for 2-DOF in-series models with hysteresis friction).The results are of both educational and prac-tical interest and may be applied for NVH analysis and testing,mechanical and aeromechanical design,and noise and vibration control in buildings. 展开更多
关键词 mechanical loss factor resonance peak ACOUSTICS VIBRATION structural failure noise NVH engineering systems
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Nested-loop Mechanism Based Modular Multilevel Converter Topology and Optimal Design 被引量:7
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作者 LIU Xinghua ZHAO Chengyong PENG Maolan GUO Chunyi ZHANG Baoshun 《中国电机工程学报》 EI CSCD 北大核心 2013年第9期I0009-I0009,共1页
普通模块化多电平换流器(modular multilevelconverter,MMC)拓扑中,因子模块数量较多,系统需采集和处理的信息量大,导致控制系统硬件构成复杂。提出一种基于循环嵌套机理的MMC拓扑,其电平输出能力得到显著提升。通过上下两组子模块的... 普通模块化多电平换流器(modular multilevelconverter,MMC)拓扑中,因子模块数量较多,系统需采集和处理的信息量大,导致控制系统硬件构成复杂。提出一种基于循环嵌套机理的MMC拓扑,其电平输出能力得到显著提升。通过上下两组子模块的协调投切,相对于普通MMC拓扑,新型拓扑输出相同电平数所需的子模块及控制设备数量大幅减少。阐述该新型拓扑的构成方式及基本参数选取原则;针对循环嵌套结构,设计相应的模块协调控制策略;分别以模块用量最小化和换流器运行损耗最小化为目标,优化设计拓扑构成方案。在RTDS中搭建换流器模型,仿真结果表明,新型拓扑具备更强的电平输出能力,并达到大幅减少子模块数量、简化控制系统硬件构成的目标。 展开更多
关键词 多电平变换器 拓扑结构 模块化 优化设计 循环机制 嵌套 电子模块 硬件结构
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Mechanism of sulfide effect on viscosity of HPAM polymer solution
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作者 康万利 周阳 +3 位作者 王志伟 孟令伟 刘述忍 白宝君 《Journal of Central South University》 SCIE EI CAS 2008年第S1期115-117,共3页
The effect of sulfide on HPAM solution viscosity was studied using BROOKFIELD DV-II viscometer,and the interaction mechanism was discussed.The HPAM solution viscosity was investigated through fully reducing sulfide by... The effect of sulfide on HPAM solution viscosity was studied using BROOKFIELD DV-II viscometer,and the interaction mechanism was discussed.The HPAM solution viscosity was investigated through fully reducing sulfide by the addition of hydrogen peroxide oxidation,and the mechanism of increasing polymer viscosity was investigated.The experimental results also show that there is a critical concentration of 15 mg/L.Below it,the loss rate of HPAM solution viscosity increases more rapidly,but becomes slowly above the critical concentration.A theoretical guidance for oilfields to prepare polymer solution using sewage-water by eliminating sulfide,and it is also importance to prepare polymer solution using sewage-water and save fresh water. 展开更多
关键词 SULFIDE HPAM solution mechanism of VISCOSITY reduction VISCOSITY loss RATE
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Contact force and mechanical loss of multistage cable under tension and bending
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作者 Yanyun Ru Huadong Yong Youhe Zhou 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2016年第5期891-904,共14页
A theoretical model for calculating the stress and strain states of cabling structures with different loadings has been developed in this paper. We solve the problem for the first- and second-stage cable with tensile ... A theoretical model for calculating the stress and strain states of cabling structures with different loadings has been developed in this paper. We solve the problem for the first- and second-stage cable with tensile or bending strain. The contact and friction forces between the strands are presented by two-dimensional contact model. Several theoretical models have been proposed to verify the results when the triplet subjected to the tensile strain, including contact force, contact stresses, and mechanical loss. It is found that loadings will affect the friction force and the mechanical loss of the triplet. The results show that the contact force and mechanical loss are dependent on the twist pitch. A shorter twist pitch can lead to higher contact force, while the trend of mechanical loss with twist pitch is complicated. The mechanical loss may be reduced by adjusting the twist pitch reasonably. The present model provides a simple analysis method to investigate the mechanical behaviors in multistage-structures under different loads. 展开更多
关键词 Contact force Friction force Tension BENDING mechanical loss
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Evaluation of corrosion resistance, mechanical integrity loss and biocompatibility of PCL/HA/TiO_(2) hybrid coated biodegradable ZM21 Mg alloy
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作者 Navdeep Singh Uma Batra +1 位作者 Kamal Kumar Anil Mahapatro 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2022年第11期3179-3204,共26页
A novel PCL/HA/TiO_(2)hybrid coating on ZM21 Mg alloy substrate has been investigated for corrosion resistance, biocompatibility and mechanical integrity loss in terms of bending, compressive and tensile strength in p... A novel PCL/HA/TiO_(2)hybrid coating on ZM21 Mg alloy substrate has been investigated for corrosion resistance, biocompatibility and mechanical integrity loss in terms of bending, compressive and tensile strength in physiological media. The prepared hybrid coating was dip coated over ZM21 from HA/TiO_(2)and PCL solutions followed by creating a microporous PCL layer by utilizing Non-solvent Induced Phase Separation(NIPS) technique. The electrochemical measurement and in-vitro degradation study in SBF after 28 days showed that the PCL/HA/TiO_(2) hybrid coating reduced H2 evolution rate, weight loss, and corrosion rate by 64, 116 and 118 times respectively, as compared to uncoated ZM21 samples. The surface studies carried out using SEM-EDX, FTIR and XRD revealed formation of highly stable 3d flower-like HA crystals with Ca/P ratio of 1.60 in the PCL micropores. This dense apatite growth effectively protected the PCL/HA/TiO_(2)hybrid coated samples to maintain the good mechanical integrity even after 28 days of immersion as compared to HA/TiO_(2)composite coated, As-polished(A/P) and As-machined(A/M) samples. The failure analysis of samples under mechanical loading were performed using SEM-BSE-EBSD.The in-vitro cellular viability of L929 fibroblast cells on PCL/HA/TiO_(2)hybrid coating was found 50.47% higher with respect to control group,whereas bacterial viability was supressed by 57.15 and 62.35% against gram-positive Staphylococcus aureus and gram-negative Escherichia coli bacterial models. The comprehensive assessment indicates PCL/HA/TiO_(2)hybrid coating as a suitable candidate to delay early degradation and mechanical integrity loss of Mg-based alloys for devising biodegradable orthopaedic implant. 展开更多
关键词 Magnesium alloy Surface modification Hybrid coating mechanical integrity loss Degradation rate BIOCOMPATIBILITY
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Synthesis of biodegradable Mg-Zn alloy by mechanical alloying: Statistical prediction of elastic modulus and mass loss using fractional factorial design
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作者 Emee Marina SALLEH Zuhailawati HUSSAIN Sivakumar RAMAKRISHNAN 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2018年第4期687-699,共13页
Biodegradable Mg-Zn alloy was synthesized using mechanical alloying where a statistical model was developed using fractional factorial design to predict elastic modulus and mass loss of the bulk alloy.The effects of m... Biodegradable Mg-Zn alloy was synthesized using mechanical alloying where a statistical model was developed using fractional factorial design to predict elastic modulus and mass loss of the bulk alloy.The effects of mechanical alloying parameters(i.e.,milling time,milling speed,ball-to-powder mass ratio and Zn content)and their interactions were investigated involving 4 numerical factors with 2 replicates,thus 16 runs of two-level fractional factorial design.Results of analysis of variance(ANOVA),regression analysis and R2 test indicated good accuracy of the model.The statistical model determined that the elastic modulus of biodegradable Mg-Zn alloy was between 40.18 and 47.88 GPa,which was improved and resembled that of natural bone(30-57 GPa).Corrosion resistance(mass loss of pure Mg,33.74 mg)was enhanced with addition of 3%-10%Zn(between 9.32 and 15.38 mg).The most significant independent variable was Zn content,and only the interaction of milling time and ball-to-powder mass ratio was significant as P-value was less than 0.05.Interestingly,mechanical properties(represented by elastic modulus)and corrosion resistance(represented by mass loss)of biodegradable Mg-Zn alloy can be statistically predicted according to the developed models. 展开更多
关键词 biodegradable Mg-Zn alloy mechanical alloying fractional factorial design elastic modulus mass loss
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Formation mechanisms of fracture plugging zone and optimization of plugging particles
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作者 LEI Shaofei SUN Jinsheng +5 位作者 BAI Yingrui LYU Kaihe ZHANG Shupei XU Chengyuan CHENG Rongchao LIU Fan 《Petroleum Exploration and Development》 CSCD 2022年第3期684-693,共10页
As formation mechanisms of plugging zone and criteria for fracture plugging remain unclear,plugging experiments and methods testing granular material mechanical properties are used to study the formation process of th... As formation mechanisms of plugging zone and criteria for fracture plugging remain unclear,plugging experiments and methods testing granular material mechanical properties are used to study the formation process of the plugging zone in fractured formations,analyze composition and ratios of different sizes of particles in the plugging zone,and reveal the essence and driving energy of the formation and damage of the plugging zone.New criteria for selecting lost circulation materials are proposed.The research results show that the formation of the plugging zone has undergone a process from inertial flow,elastic flow,to quasi-static flow.The plugging zone is composed of fracture mouth plugging particles,bridging particles and filling particles,and the proportion of the three types of particles is an important basis for designing drilling fluid loss control formula.The essence of the construction of the plugging zone is non-equilibrium Jamming phase transition.The response of the plugging zone particle system to pressure is driven by entropy force;the greater the entropy,the more stable the plugging zone.Lost circulation control formula optimized according to the new criteria has better plugging effect than the formula made according to conventional plugging rules and effectively improves the pressure-bearing capacity of the plugging zone.The research results provide a theoretical and technical basis for the lost circulation control of fractured formations. 展开更多
关键词 fractured formation drilling fluid loss plugging zone plugging mechanism plugging particles optimization criterion
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微重力导致骨质疏松的机制
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作者 向德剑 梁晓远 +5 位作者 王胜红 陈长顺 田聪 闫振兴 耿彬 夏亚一 《中国组织工程研究》 CAS 北大核心 2025年第10期2132-2140,共9页
背景:在微重力环境中骨吸收和骨形成的失衡,导致航天员出现严重的骨质流失。现有研究表明,微重力环境下的骨质流失是由多种细胞、组织和系统共同作用的结果。目的:综述微重力对不同的细胞、组织或系统产生不同的生物学效应,总结微重力... 背景:在微重力环境中骨吸收和骨形成的失衡,导致航天员出现严重的骨质流失。现有研究表明,微重力环境下的骨质流失是由多种细胞、组织和系统共同作用的结果。目的:综述微重力对不同的细胞、组织或系统产生不同的生物学效应,总结微重力导致骨质疏松发生的机制。方法:在Pub Med、Web of Science和Cochrane图书馆数据库检索2000-2023年的相关文献,纳入标准为与微重力导致骨质疏松相关的组织工程研究和基础研究的所有文章,最终对85篇文献进行综述。结果与结论:(1)在微重力环境下,骨髓间充质干细胞更倾向于向成脂细胞分化,减少向成骨细胞分化,而微重力环境中的造血干细胞则更倾向于分化为破骨细胞,减少向红系分化;同时,微重力抑制成骨细胞增殖和分化、促进成骨细胞凋亡、改变细胞形态及降低成骨细胞矿化能力,显著增加破骨细胞数量和活性并且阻碍成骨细胞向骨细胞分化,促进骨细胞的凋亡。(2)在微重力环境下,人体会出现骨骼肌萎缩、微血管重塑、骨微循环障碍及内分泌紊乱等组织或系统的变化,这些变化会导致骨骼微环境下机械应力卸载,血液灌注不足以及钙循环紊乱等,对骨质疏松的发生产生了重要的影响。(3)目前,微重力导致骨质疏松的机制较为复杂,通过更深入的研究这些生理机制对于确保航天员在长期太空任务中的健康至关重要,并为预防和治疗骨质疏松症提供了理论依据。 展开更多
关键词 微重力 成骨细胞 骨形成 破骨细胞 骨吸收 骨质流失 机械卸载 骨稳态 增殖分化 细胞凋亡
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Flow Loss Mechanism in a Supercritical Carbon Dioxide Centrifugal Compressor at Low Flow Rate Conditions 被引量:3
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作者 YANG Zimu JIANG Hongsheng +5 位作者 ZHUGE Weilin CAI Ruikai YANG Mingyang CHEN Haoxiang QIAN Yuping ZHANG Yangjun 《Journal of Thermal Science》 SCIE EI CSCD 2024年第1期114-125,共12页
With the advantages of high efficiency and compact structure,supercritical carbon dioxide(sC02)Brayton cycles have bright prospects for development in energy conversion field.As one of the core components of the power... With the advantages of high efficiency and compact structure,supercritical carbon dioxide(sC02)Brayton cycles have bright prospects for development in energy conversion field.As one of the core components of the power cycle,the centrifugal compressor tends to operate near the critical point(304.13 K,7.3773 MPa).Normally,the compressor efficiency increases as the inlet temperature decreases.When the inlet temperature is close to the critical point,the density increases sharply as the temperature decreases,which results in quickly decreasing of volume flow rate and efficiency reducing.The flow loss mechanism of the sCO_(2) compressor operating at low flow rate is studied in this paper.Computational fluid dynamics(CFD) simulations for sCO_(2)compressor were carried out at various inlet temperatures and various mass flow rates.When the sCO_(2)compressor operates at low volume flow rate,the flow loss is generated mainly on the suction side near the trailing edge of the blade.The flow loss is related to the counterclockwise vortexes generated on the suction side of the main blade.The vortexes are caused by the flow separation in the downstream region of the impeller passage,which is different from air compressors operating at low flow rates.The reason for this flow separation is that the effect of Coriolis force is especially severe for the sCO_(2) fluid,compared to the viscous force and inertial force.At lower flow rates,with the stronger effect of Coriolis force,the direction of relative flow velocity deviates from the direction of radius,resulting in its lower radial component.The lower radial relative flow velocity leads to severe flow separation on the suction side near the trailing edge of the main blade. 展开更多
关键词 supercritical CO_(2) centrifugal compressor flow loss mechanism Coriolis force
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A preliminary study of the mechanism of compound hearing loss caused by ototoxic drugs combined with impulse noise
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作者 Xin Qiu Qing‐qing Jiang +2 位作者 Wei‐wei Guo Ning Yu Shi‐ming Yang 《iLABMED》 2024年第1期38-52,共15页
Background:Hearing loss(HL)is becoming increasingly common and is more commonly caused by noise,ototoxic substances,or a combination of ototoxic factors.However,so far,few studies have examined the mechanism by which ... Background:Hearing loss(HL)is becoming increasingly common and is more commonly caused by noise,ototoxic substances,or a combination of ototoxic factors.However,so far,few studies have examined the mechanism by which compound factors cause HL.The only relevant study is about occupational ototoxic substances combined with environmental noise at 85-110 dB SPL.In this study,to address the shortcomings of existing research,we innovatively focused on HL induced by loud noise(impulse noise,>160 dB SPL)combined with common ototoxic drugs.The aim of this study was to establish and validate a mature animal model,and then to compare the characteristics of audiology,pathomorphology and molecular features,and to preliminarily predict pathogenesis in compound HL.Materials and Methods:We selected guinea pigs to construct in vivo HL model groups for different extents of exposure,including a blank control group,a single-drug group,a single-impulse noise group,and a compound group.The animal model of the mature compound HL group was established using gentamicin combined with impulse noise.We then performed audio-logical and pathological verification.We analyzed the auditory brainstem response(ABR),pathological morphology of the cochlea,and molecules(including important self-radicals,cytokines,and apoptosis signal trans-duction pathway proteins in the pathogenesis of drug-and noise-induced HL),compared the effect of different extents of exposure on HL,and preliminarily predict the pathogenic mechanism of compound HL.Results:Four groups of animal models were established successfully and verified by audiology and pathology.Regarding audiology,there were no sig-nificant differences in the ABR thresholds before exposure(p>0.05),but differences emerged among the groups after exposure.Notably,after 3,7,and 14 days of exposure,there were significant differences in the ABR thresholds between the compound group and both the drug and noise groups(p<0.01),and after 14 days,the HL of the compound group was much more severe(greater than the linear sum of single-factor HL group).Regarding the patho-morphology,compared with the control group,the cochleae were damaged to different degrees in the factor exposure groups.The drug group had the least severe HL,the noise group had serious HL(p<0.05),and the compound group had the most severe HL(p<0.01).The compound group's damage was greater than the linear sum of the single-factor group in many ways,such as the loss and damage of hair cells and cilia,disturbed morphology and arrangement of hair cells,protein metabolism,cell function,and structural defects on the epidermal plate(p<0.01).From a molecular perspective,the trend was similar to pathology and audiology,and the synergistic effect of ototoxic drugs and impulse noise significantly increased cytokine levels(IL-6,ICAM-1,8-OHDG,IL-1,and TNF-α),free radicals Malondialdehyde([MDA],▪OH,LPO,O•2ˉ),and the apoptosis signal transduction pathway protein.There were significant differences between the compound group and single-factor groups(p<0.05).Conclusion:Gentamicin,impulse noise,and compound factors were used to induce HL in animal models,which were verified by audiology and pathology,laying a foundation for future studies.After constructing the animal models,we found that 50 mg/kg of gentamicin for 10 days was a subinjury dose,and 50�impulse noise caused partial HL,but the two factors combined had a significant synergistic ototoxicity effect,which increased the level of oxidative stress and the waterfall response of inflammatory cytokines in the cochleae and enhanced the expression of apoptosis-related proteins,resulting in syn-ergistic pathomorphological and audiological injury.We preliminarily analyzed the pathogenic mechanism of compound HL,establishing the basis for further study of the mechanism,prevention,and treatment of this increasing global problem. 展开更多
关键词 auditory brainstem response GENTAMICIN hearing loss impulse noise molecular mechanisms PATHOMORPHOLOGY
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