A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combin...A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combined with 3D advanced numerical simulations performed using the IMPETUS Afea? software yielded the conclusions.The experimental verification proved that slight differences in the pitch-andyaw angles of a projectile upon an impact caused different damage types to the projectile’s core.The residual velocities predicted numerically were close to the experimental values and the calculated core deviations were in satisfactory agreement with the experimental results.An extended matrix of the core deviation angles with combinations of pitch-and-yaw upon impact angles was subsequently built on the basis of the numerical study.The presented experimental and numerical investigation examined thoroughly the influence of the initial pitch and yaw angles on the after-perforation projectile’s performance.展开更多
This paper developed a comprehensive evaluation system that was able to quantify the levels of high-quality development across the cities within the Chengdu-Chongqing economic circle,and investigate the impact that di...This paper developed a comprehensive evaluation system that was able to quantify the levels of high-quality development across the cities within the Chengdu-Chongqing economic circle,and investigate the impact that digital finance had on the cities’high-quality development and the underlying mechanisms through which it achieved this.This comprehensive evaluation system was constructed using statistical data from these cities for the period 2014 to 2020 while also taking China’s high-quality development philosophy into account.The key findings revealed that:(a)Digital finance was able to significantly promote high-quality development in the Chengdu-Chongqing economic circle;(b)Digital finance had a significant positive effect in promoting innovative,coordinated,green,open,and shared development;(c)Digital finance was able to stimulate the high-quality development in the Chengdu-Chongqing economic circle by boosting entrepreneurial dynamism;(d)Digital finance had a significant impact on the high-quality development of the axis areas,while its impact was less discernible in non-axis areas.The insights from this research offer a deeper understanding of the factors that drive high-quality development,the role digital finance plays,and the mechanisms through which digital finance is able to propel high-quality development at the city cluster scale.展开更多
Coordinative development across various systems,particularly the economic,social,cultural,and human resources subsystems,is a key aspect of urban sustainability and has a direct impact on the quality of urbanization.T...Coordinative development across various systems,particularly the economic,social,cultural,and human resources subsystems,is a key aspect of urban sustainability and has a direct impact on the quality of urbanization.The Hangzhou Metropolitan Circle,comprising Hangzhou City,Huzhou City,Jiaxing City,and Shaoxing City,was the first metropolitan circle approved by the National Development and Reform Commission(NDRC)as a demonstration of economic transformation in China.To evaluate the coupling coordination degree of the four cities and analyze the coordinative development in three systems(including digital economy,regional innovation,and talent employment),we collected panel data during 2015–2022 from these four cities.The development level of the three systems was evaluated by the standard deviation method and comprehensive development index.The results are as follows:(1)the level of coupling coordinated development of the three systems in the Hangzhou Metropolitan Circle was relatively low;(2)the coupling coordination degree of the four cities in the Hangzhou Metropolitan Circle showed significant regional differences,among which Hangzhou City was in the leading position,and Huzhou,Jiaxing,and Shaoxing cities made steady but slow progress in the coupling development of the three systems;and(3)the development of digital economy and talent employment needs to be strengthened.This study contributes to the coordinative development of Hangzhou Metropolitan Circle by innovatively focusing on the coupling coordination relationship among digital economy,regional innovation,and talent employment,which also meets the industrial layout of Hangzhou Metropolitan Circle.In this way,the optimal allocation and sustainable development of digital economy,regional innovation,and talent employment in the Hangzhou Metropolitan Circle can be achieved.展开更多
Building a 15-minute radius livelihood service circle from the needs of residents is a topdown process of optimizing urban layout and promoting high-quality development implemented by the government.In September 2022,...Building a 15-minute radius livelihood service circle from the needs of residents is a topdown process of optimizing urban layout and promoting high-quality development implemented by the government.In September 2022,Xicheng District of Beijing served as a national pilot of the 15-minute radius livelihood service circle.Based on the data of POI,urban walking network and building outline,this paper studies the coverage of commercial service facilities in the 15-minute radius livelihood service circle of Chunshu Street by using kernel density analysis and urban network analysis tools.The research shows that the commercial facilities are concentrated in Zhuangsheng Square and Dazhalan commercial district.There are large gaps in housekeeping and couriers logistics facilities,which need to be further improved.展开更多
Objective: To explore the effect of evidence-based quality control circle (QCC) in improving the implementation rate of airway management measures in adult critically ill patients. Methods: Based on the Joanna Briggs ...Objective: To explore the effect of evidence-based quality control circle (QCC) in improving the implementation rate of airway management measures in adult critically ill patients. Methods: Based on the Joanna Briggs Institute (JBI) evidence-based health care model, the best evidence of airway management in adult critically ill patients was obtained and applied to the clinic. Results: The total implementation rate of airway management measures in adult critically ill patients increased from 23.62% before the implementation of quality control circle to 88.82%, and the pulmonary infection rate in critically ill patients decreased from 42.31% to 21.74%, with statistical significance between the two groups (P 0.05). Conclusion: Evidence-based quality control circle activities can standardize the practice standards of airway management in critically ill patients, reduce the occurrence of patients’ airway related complications, and improve clinical outcomes.展开更多
Tetrahydrofuran(THF) extract of coal tar pitch(CTP) was used instead of blending CTP with pretreated pyrolysis fuel oil to prepare an isotropic pitch precursor with excellent spinnability for general-purpose carbon fi...Tetrahydrofuran(THF) extract of coal tar pitch(CTP) was used instead of blending CTP with pretreated pyrolysis fuel oil to prepare an isotropic pitch precursor with excellent spinnability for general-purpose carbon fibre through bromination-dehydrobromination. The feasibility and effectiveness of synthesising an isotropic pitch precursor derived from THF-soluble(CTP-THFs) is demonstrated in this study.The results show that CTP-THFs contains more light components than CTP;CTP-THFs and CTP monomer proportions were 62.52% and 45.32%, respectively. However, based on comparisons of CTP-THFsBr0 and CTPBr0 characterisations, CTP-THFs exhibits better polycondensation than CTP. Bromination-dehydrobro mination promotes polycondensation of pitch precursors, leading to greater carbon aromaticity in CTP-THFsBr5, CTP-THFsBr10, and CTP-THFsBr15 than that in CTP-THFsBr0 and CTPBr0. CTP-THFsBr5 and CTP-THFsBr10 have excellent spinnability even with softening points as high as 230 ℃. The pericondensed carbon and carbon aromaticity of CTP-THFsBr5 and CTP-THFsBr10 are high owing to the higher degree of polycondensation;however, they still possess a more linear molecular structure. The as-prepared carbon fibre exhibits homogeneity and uniformity, and the mechanical performance is comparable with that of commercial general-purpose carbon fibre products.展开更多
To improve the electrochemical performance of graphite anode materials,pitches with various softening points(150℃,180℃,200℃,and 250℃)were prepared from ethylene tar and used to coat graphite through a liquid coati...To improve the electrochemical performance of graphite anode materials,pitches with various softening points(150℃,180℃,200℃,and 250℃)were prepared from ethylene tar and used to coat graphite through a liquid coating process.The effects of the softening point of the pitch and the coating amount on the microstructure and electrochemical properties of graphite were studied by methods including thermogravimetric analysis,X-ray diffraction,Raman spectroscopy,surface area analysis,scanning electron microscopy,transmission electron microscopy,and electrochemical testing.The graphite particles were coated uniformly by the pyrolytic carbon in the pitch.The coating changed the degree of graphitization,decreased the average specific surface area,and improved the electrochemical performance significantly.The best battery anode performance was obtained when the mass ratio of pitch to graphite was 10%,the heat treatment temperature was 1100℃,and the softening point of the pitch was 250℃.Under the optimum conditions,the irreversible capacity loss in the first cycle at 0.1 C was only 23 mAh/g,and the first Coulombic efficiency reached 94.2%.The capacity retention rate was 98.3%after 100 charge-discharge cycles at 0.1 C.展开更多
Coupled phase oscillators are adopted as powerful platforms in studying synchrony behaviors emerged in various systems with rhythmic dynamics. Much attention has been focused on coupled time-continuous oscillators des...Coupled phase oscillators are adopted as powerful platforms in studying synchrony behaviors emerged in various systems with rhythmic dynamics. Much attention has been focused on coupled time-continuous oscillators described by differential equations. In this paper, we study the synchronization dynamics of networks of coupled circle maps as the discrete version of the Kuramoto model. Despite of its simplicity in mathematical form, it is found that discreteness may induce many interesting synchronization behaviors. Multiple synchronization and desynchronization transitions of both phases and frequencies are found with varying the coupling among circle-map oscillators. The mechanisms of these transitions are interpreted in terms of the mean-field approach, where collective bifurcation cascades are revealed for coupled circle-map oscillators.展开更多
In order to obtain the microwave absorption(MA)materials with light weight,high efficiency and tunable properties,the carbonized mesophase pitch(CMP)with the variation in carbonization temperatures and particle sizes ...In order to obtain the microwave absorption(MA)materials with light weight,high efficiency and tunable properties,the carbonized mesophase pitch(CMP)with the variation in carbonization temperatures and particle sizes were prepared and characterized.The carbonization temperature mainly controlled the graphitization degree of the CMP to affect their conductive loss.The carbon residues were generated on the CMP surface when the temperature was higher than 700℃,which contributed significantly to the polarization loss of the CMP.For scale regulation,the segregation between the particles in the paraffin ring caused by the reduction particles of CMP carbonization at 750℃(750 CMP)resulted in a significant reduction in conductive losses while improving their impedance matching.The 750 CMP over 300 mesh sieved had the strongest MA properties of-53 d B at 3.4 GHz within 5.5 mm.Moreover,the prepared CMPs were multi-layer compounded and optimized by CST microwave studio.The synergistic effect derived from the improved impedance matching and the enhanced interfacial polarization resulted in significant reflection loss in multi-layer CMP.Overall,these findings lead to the systematically regulation of carbon-based materials for MA,showing an attractive application prospect for the preparation of high-performance MA materials.展开更多
There are numerous methods and additives available to improve the durability and quality of road bitumen. A coal tar obtained by coal coking was distilled in a laboratory into fractions of initial boiling point IBP-18...There are numerous methods and additives available to improve the durability and quality of road bitumen. A coal tar obtained by coal coking was distilled in a laboratory into fractions of initial boiling point IBP-180℃ (gasoline-like fuel), 180℃ - 360℃ (diesel-like fuel), and >360℃ (residue or coal tar pitch). The coal tar pitch was added into road bitumen by up to 1 - 5 wt% and investigated the alteration of physical and chemical properties. The physico-mechanical properties of coal tar pitch and bitumen blends, as well as the chemical group composition, were determined using standard techniques (MNS) and the SARA method, respectively. Results of 3% coal tar pitch addition into bitumen enhanced ductility by 12.4% and softening point by 1.6℃. We found that blending with bitumen coal tar pitch as a modifier could improve bitumen properties.展开更多
The microstructures of carbon precursors significantly affect the electrochemical performance of Si/C composite anodes.However,the interaction between Si and carbon materials with different structures is still unclear...The microstructures of carbon precursors significantly affect the electrochemical performance of Si/C composite anodes.However,the interaction between Si and carbon materials with different structures is still unclear.Pitch-based materials undergoing different thermal treatments are superior sources for synthesizing carbons with different structures.Herein,different types of mesophase pitch(domain,flow-domain and mosaic structure) obtained from controllable thermal condensation are utilized to prepare Si/C composite materials and the corresponding models are established through finite element simulation to explore the correlation between the lithium storage properties of Si/C composites and the structures of carbon materials.The results indicate that the flow-domain texture pitch P2 has a better ability to buffer the volume expansion of silicon particles for its highly ordered arrangement of carbon crystallites inside could disperse the swelling stress uniformly alongside the particle surface.The sample Si@P2 exhibits the highest capacity of 1328 mA h/g after 200 cycles at a current density of 0.1 A/g as well as the best rate performance and stability.While sample Si@P3 in which the mosaic texture pitch P3 composed of random orientation of crystallites undergoes the fastest capacity decay.These findings suggest that highly ordered carbon materials are more suitable for the synthesis of Si/C composite anodes and provide insights for understanding the interaction between carbon and silicon during the charging/discharging process.展开更多
To ensure wind turbine(WT)safe operations and improve the utilization rate of wind energy,effective evaluation of the operation state of the pitch system is critical.Therefore,a new method was proposed to evaluate the...To ensure wind turbine(WT)safe operations and improve the utilization rate of wind energy,effective evaluation of the operation state of the pitch system is critical.Therefore,a new method was proposed to evaluate the operation state of the pitch system of WT based on fuzzy comprehensive evaluation.Firstly,based on SCADA data,the working state of the pitch system under rated power state and power state of WT were analyzed.Secondly,through the analysis of characteristic parameters and physical mechanism of the pitch system,the consistency principle of characteristic parameters,the stability principle of power under rated state,and the stability principle of blade angle underpowered state were obtained.Next,based on the aforementioned principles,the evaluation indexes were established,and the fuzzy comprehensive evaluation method was used to establish the operation state evaluation model of the pitch system under rated power state and under power state of the WT.Finally,an example was provided to verify the effectiveness of the method.The evaluation model established in this study can be used as a technical reference for the online monitoring of WT pitch systems to ensure the safe and stable operation of WTs.展开更多
Squaring the circle is one of the oldest challenges in mathematical geometry. In 1882, it was proven that π was transcendental, and the task of squaring the circle was considered impossible. Demonstrating that squari...Squaring the circle is one of the oldest challenges in mathematical geometry. In 1882, it was proven that π was transcendental, and the task of squaring the circle was considered impossible. Demonstrating that squaring the circle was not possible took place before discovering quantum mechanics. The purpose of this paper is to show that it is actually possible to square the circle when taking into account the Heisenberg uncertainty principle. The conclusion is clear: it is possible to square the circle when taking into account the Heisenberg uncertainty principle.展开更多
The pitch angle distributions of ions and electrons can be affected by various processes;thus,they can serve as an important indicator of the physical mechanisms driving the dynamics of space plasmas.From observations...The pitch angle distributions of ions and electrons can be affected by various processes;thus,they can serve as an important indicator of the physical mechanisms driving the dynamics of space plasmas.From observations from the Mars Ion and Neutral Particle Analyzer onboard the Tianwen-1 orbiter,we calculated the pitch angle distributions of protons in the Martian induced magnetosphere by using information from the magnetohydrodynamically simulated magnetic field,and we statistically analyzed the spatial occurrence pattern of different types of pitch angle distributions.Even though no symmetrical features were seen in the dataset,we found the dominance of the field-aligned distribution type over the energy range from 188 to 6232 eV.Maps of the occurrence rate showed the preferential presence of a trapped-like distribution at the lower altitudes of the surveyed nightside region.Although our results are more or less restricted by the adopted magnetic field,they indicate the complexity of the near-Mars proton pitch angle distributions and infer the possibility of wave–particle interactions in the Martian induced magnetosphere.展开更多
In the first-tier cities,subway has become an important carrier and life focus of people’s daily travel activities.By studying the distribution of POIs of public service facilities around Metro Line 10,using GIS to q...In the first-tier cities,subway has become an important carrier and life focus of people’s daily travel activities.By studying the distribution of POIs of public service facilities around Metro Line 10,using GIS to quantitatively analyze the surrounding formats of subway stations,discussing the functional attributes of subway stations,and discussing the distribution of urban functions from a new perspective,this paper provided guidance and advice for the construction of service facilities.展开更多
This paper presents a graphical procedure for the squaring of a circle of any radius. This procedure, which is based on a novel application of the involute profile, when applied to a circle of arbitrary radius (using ...This paper presents a graphical procedure for the squaring of a circle of any radius. This procedure, which is based on a novel application of the involute profile, when applied to a circle of arbitrary radius (using only an unmarked ruler and a compass), produced a square equal in area to the given circle, which is 50 cm<sup>2</sup>. This result was a clear demonstration that not only is the construction valid for the squaring of a circle of any radius, but it is also capable of achieving absolute results (independent of the number pi (π), in a finite number of steps), when carried out with precision.展开更多
Business English reading teaching under the mode of“literature circles”focuses on cultivating students’autonomy in reading,group cooperation,and the exchange of ideas among group members.In this teaching mode,teach...Business English reading teaching under the mode of“literature circles”focuses on cultivating students’autonomy in reading,group cooperation,and the exchange of ideas among group members.In this teaching mode,teachers are no longer the masters of the reading classroom,but the helpers,participants,and researchers in the process of students’reading.The reconstruction of teachers’role can promote the benign development of relationship not only between teachers and students,but also between students and students,inject new impetus and vitality into the classroom,and improve students’reading literacy.展开更多
Background:Good adherence to post-operative exercise is crucial for long-term exercise intervention programs aimed at improving compliance,motivation for functional exercise,and quality of life among breast cancer pat...Background:Good adherence to post-operative exercise is crucial for long-term exercise intervention programs aimed at improving compliance,motivation for functional exercise,and quality of life among breast cancer patients.This study aims to evaluate the application effect of quality control circles on postoperative functional exercise compliance in breast neoplasm patients.Methods:A comprehensive search was conducted in CNKI,Wanfang,VIP,CBM,PubMed,Cochrane Library,Web of Science and CINAHL databases from their establishment to May 06,2023.Manual search and backtracking of relevant literature were also conducted.The search terms included a combination of subject terms and free words.Meta-analysis was performed using RevMan 5.4 software on eligible literature.Results:Initially,517 papers were retrieved,and after removing duplicates 238 papers using NoteExpress software,279 titles and abstracts were reviewed.Subsequently,225 non-compliant papers were excluded,leaving 54 full texts to be read.After excluding 38 non-compliant papers,16 eligible papers were included for Meta-analysis.These papers comprised a total of 1,342 patients(679 in the test group and 663 in the control group).The heterogeneity test using a fixed effects model showed P=0.22 and I2=21%.The Meta-analysis results demonstrated that the implementation of quality control circles alongside usual care significantly improved compliance with postoperative functional exercise in breast cancer patients(odds ratio=6.68,95%confidence interval(4.97,8.98),P<0.00001).Conclusion:Quality control circles activities can effectively enhance compliance with post-operative functional exercise among breast cancer patients,aiding in the recovery of affected limb function,improvement of self-care ability,and early reintegration into society and normal life,thereby enhancing quality of life.It is important to continually accumulate experience in applying relevant quality control circles activities in clinical work and promptly enhance the level of care accordingly,as the functional exercise of breast cancer patients after surgery involves a long-term and gradual improvement process.展开更多
文摘A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combined with 3D advanced numerical simulations performed using the IMPETUS Afea? software yielded the conclusions.The experimental verification proved that slight differences in the pitch-andyaw angles of a projectile upon an impact caused different damage types to the projectile’s core.The residual velocities predicted numerically were close to the experimental values and the calculated core deviations were in satisfactory agreement with the experimental results.An extended matrix of the core deviation angles with combinations of pitch-and-yaw upon impact angles was subsequently built on the basis of the numerical study.The presented experimental and numerical investigation examined thoroughly the influence of the initial pitch and yaw angles on the after-perforation projectile’s performance.
文摘This paper developed a comprehensive evaluation system that was able to quantify the levels of high-quality development across the cities within the Chengdu-Chongqing economic circle,and investigate the impact that digital finance had on the cities’high-quality development and the underlying mechanisms through which it achieved this.This comprehensive evaluation system was constructed using statistical data from these cities for the period 2014 to 2020 while also taking China’s high-quality development philosophy into account.The key findings revealed that:(a)Digital finance was able to significantly promote high-quality development in the Chengdu-Chongqing economic circle;(b)Digital finance had a significant positive effect in promoting innovative,coordinated,green,open,and shared development;(c)Digital finance was able to stimulate the high-quality development in the Chengdu-Chongqing economic circle by boosting entrepreneurial dynamism;(d)Digital finance had a significant impact on the high-quality development of the axis areas,while its impact was less discernible in non-axis areas.The insights from this research offer a deeper understanding of the factors that drive high-quality development,the role digital finance plays,and the mechanisms through which digital finance is able to propel high-quality development at the city cluster scale.
基金supported by the Ningbo Polytechnic Industry-Education Integration Research Project(NZ23CJ05Z)the Ningbo Municipal Philosophy and Social Science Project(G2023-2-Z11)the Soft Science Project of Zhejiang Science and Technology Department,China(2024C35096).
文摘Coordinative development across various systems,particularly the economic,social,cultural,and human resources subsystems,is a key aspect of urban sustainability and has a direct impact on the quality of urbanization.The Hangzhou Metropolitan Circle,comprising Hangzhou City,Huzhou City,Jiaxing City,and Shaoxing City,was the first metropolitan circle approved by the National Development and Reform Commission(NDRC)as a demonstration of economic transformation in China.To evaluate the coupling coordination degree of the four cities and analyze the coordinative development in three systems(including digital economy,regional innovation,and talent employment),we collected panel data during 2015–2022 from these four cities.The development level of the three systems was evaluated by the standard deviation method and comprehensive development index.The results are as follows:(1)the level of coupling coordinated development of the three systems in the Hangzhou Metropolitan Circle was relatively low;(2)the coupling coordination degree of the four cities in the Hangzhou Metropolitan Circle showed significant regional differences,among which Hangzhou City was in the leading position,and Huzhou,Jiaxing,and Shaoxing cities made steady but slow progress in the coupling development of the three systems;and(3)the development of digital economy and talent employment needs to be strengthened.This study contributes to the coordinative development of Hangzhou Metropolitan Circle by innovatively focusing on the coupling coordination relationship among digital economy,regional innovation,and talent employment,which also meets the industrial layout of Hangzhou Metropolitan Circle.In this way,the optimal allocation and sustainable development of digital economy,regional innovation,and talent employment in the Hangzhou Metropolitan Circle can be achieved.
文摘Building a 15-minute radius livelihood service circle from the needs of residents is a topdown process of optimizing urban layout and promoting high-quality development implemented by the government.In September 2022,Xicheng District of Beijing served as a national pilot of the 15-minute radius livelihood service circle.Based on the data of POI,urban walking network and building outline,this paper studies the coverage of commercial service facilities in the 15-minute radius livelihood service circle of Chunshu Street by using kernel density analysis and urban network analysis tools.The research shows that the commercial facilities are concentrated in Zhuangsheng Square and Dazhalan commercial district.There are large gaps in housekeeping and couriers logistics facilities,which need to be further improved.
文摘Objective: To explore the effect of evidence-based quality control circle (QCC) in improving the implementation rate of airway management measures in adult critically ill patients. Methods: Based on the Joanna Briggs Institute (JBI) evidence-based health care model, the best evidence of airway management in adult critically ill patients was obtained and applied to the clinic. Results: The total implementation rate of airway management measures in adult critically ill patients increased from 23.62% before the implementation of quality control circle to 88.82%, and the pulmonary infection rate in critically ill patients decreased from 42.31% to 21.74%, with statistical significance between the two groups (P 0.05). Conclusion: Evidence-based quality control circle activities can standardize the practice standards of airway management in critically ill patients, reduce the occurrence of patients’ airway related complications, and improve clinical outcomes.
基金the financial support provided by the National Natural Science Foundation of China (22008254)the Fundamental Research Funds for the Central Universities (2020XJHH01)+1 种基金the National Training Program of Innovation and Entrepreneurship for Undergraduates (C202003309)China University of Mining and Technology (Beijing) Yueqi Outstanding Scholar Project (2020JCB02)。
文摘Tetrahydrofuran(THF) extract of coal tar pitch(CTP) was used instead of blending CTP with pretreated pyrolysis fuel oil to prepare an isotropic pitch precursor with excellent spinnability for general-purpose carbon fibre through bromination-dehydrobromination. The feasibility and effectiveness of synthesising an isotropic pitch precursor derived from THF-soluble(CTP-THFs) is demonstrated in this study.The results show that CTP-THFs contains more light components than CTP;CTP-THFs and CTP monomer proportions were 62.52% and 45.32%, respectively. However, based on comparisons of CTP-THFsBr0 and CTPBr0 characterisations, CTP-THFs exhibits better polycondensation than CTP. Bromination-dehydrobro mination promotes polycondensation of pitch precursors, leading to greater carbon aromaticity in CTP-THFsBr5, CTP-THFsBr10, and CTP-THFsBr15 than that in CTP-THFsBr0 and CTPBr0. CTP-THFsBr5 and CTP-THFsBr10 have excellent spinnability even with softening points as high as 230 ℃. The pericondensed carbon and carbon aromaticity of CTP-THFsBr5 and CTP-THFsBr10 are high owing to the higher degree of polycondensation;however, they still possess a more linear molecular structure. The as-prepared carbon fibre exhibits homogeneity and uniformity, and the mechanical performance is comparable with that of commercial general-purpose carbon fibre products.
基金This work was financially supported by the Research Program of China Petrochemical Corporation(SINOPEC 121023).
文摘To improve the electrochemical performance of graphite anode materials,pitches with various softening points(150℃,180℃,200℃,and 250℃)were prepared from ethylene tar and used to coat graphite through a liquid coating process.The effects of the softening point of the pitch and the coating amount on the microstructure and electrochemical properties of graphite were studied by methods including thermogravimetric analysis,X-ray diffraction,Raman spectroscopy,surface area analysis,scanning electron microscopy,transmission electron microscopy,and electrochemical testing.The graphite particles were coated uniformly by the pyrolytic carbon in the pitch.The coating changed the degree of graphitization,decreased the average specific surface area,and improved the electrochemical performance significantly.The best battery anode performance was obtained when the mass ratio of pitch to graphite was 10%,the heat treatment temperature was 1100℃,and the softening point of the pitch was 250℃.Under the optimum conditions,the irreversible capacity loss in the first cycle at 0.1 C was only 23 mAh/g,and the first Coulombic efficiency reached 94.2%.The capacity retention rate was 98.3%after 100 charge-discharge cycles at 0.1 C.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11875135)。
文摘Coupled phase oscillators are adopted as powerful platforms in studying synchrony behaviors emerged in various systems with rhythmic dynamics. Much attention has been focused on coupled time-continuous oscillators described by differential equations. In this paper, we study the synchronization dynamics of networks of coupled circle maps as the discrete version of the Kuramoto model. Despite of its simplicity in mathematical form, it is found that discreteness may induce many interesting synchronization behaviors. Multiple synchronization and desynchronization transitions of both phases and frequencies are found with varying the coupling among circle-map oscillators. The mechanisms of these transitions are interpreted in terms of the mean-field approach, where collective bifurcation cascades are revealed for coupled circle-map oscillators.
基金supported by Sichuan Science and Technology Program,Grant No.2022YFG0111the Postdoctoral Innovative Talent Support Program(Grant No.BX20190220)the State Key Laboratory of Polymer Materials Engineering(Grant No.sklpme2019-2-02)for financial support。
文摘In order to obtain the microwave absorption(MA)materials with light weight,high efficiency and tunable properties,the carbonized mesophase pitch(CMP)with the variation in carbonization temperatures and particle sizes were prepared and characterized.The carbonization temperature mainly controlled the graphitization degree of the CMP to affect their conductive loss.The carbon residues were generated on the CMP surface when the temperature was higher than 700℃,which contributed significantly to the polarization loss of the CMP.For scale regulation,the segregation between the particles in the paraffin ring caused by the reduction particles of CMP carbonization at 750℃(750 CMP)resulted in a significant reduction in conductive losses while improving their impedance matching.The 750 CMP over 300 mesh sieved had the strongest MA properties of-53 d B at 3.4 GHz within 5.5 mm.Moreover,the prepared CMPs were multi-layer compounded and optimized by CST microwave studio.The synergistic effect derived from the improved impedance matching and the enhanced interfacial polarization resulted in significant reflection loss in multi-layer CMP.Overall,these findings lead to the systematically regulation of carbon-based materials for MA,showing an attractive application prospect for the preparation of high-performance MA materials.
文摘There are numerous methods and additives available to improve the durability and quality of road bitumen. A coal tar obtained by coal coking was distilled in a laboratory into fractions of initial boiling point IBP-180℃ (gasoline-like fuel), 180℃ - 360℃ (diesel-like fuel), and >360℃ (residue or coal tar pitch). The coal tar pitch was added into road bitumen by up to 1 - 5 wt% and investigated the alteration of physical and chemical properties. The physico-mechanical properties of coal tar pitch and bitumen blends, as well as the chemical group composition, were determined using standard techniques (MNS) and the SARA method, respectively. Results of 3% coal tar pitch addition into bitumen enhanced ductility by 12.4% and softening point by 1.6℃. We found that blending with bitumen coal tar pitch as a modifier could improve bitumen properties.
基金financial support from the National Key Research and Development Programme (2018YFC1801901)the National Natural Science Foundation of China (21808115, 22108309, 52172093)+1 种基金the Key Research and Development Project (Major Project of Scientific and Technological Innovation) of Shandong Province (2020CXGC010308)the Taishan Scholar Program of Shandong (ts20190919)。
文摘The microstructures of carbon precursors significantly affect the electrochemical performance of Si/C composite anodes.However,the interaction between Si and carbon materials with different structures is still unclear.Pitch-based materials undergoing different thermal treatments are superior sources for synthesizing carbons with different structures.Herein,different types of mesophase pitch(domain,flow-domain and mosaic structure) obtained from controllable thermal condensation are utilized to prepare Si/C composite materials and the corresponding models are established through finite element simulation to explore the correlation between the lithium storage properties of Si/C composites and the structures of carbon materials.The results indicate that the flow-domain texture pitch P2 has a better ability to buffer the volume expansion of silicon particles for its highly ordered arrangement of carbon crystallites inside could disperse the swelling stress uniformly alongside the particle surface.The sample Si@P2 exhibits the highest capacity of 1328 mA h/g after 200 cycles at a current density of 0.1 A/g as well as the best rate performance and stability.While sample Si@P3 in which the mosaic texture pitch P3 composed of random orientation of crystallites undergoes the fastest capacity decay.These findings suggest that highly ordered carbon materials are more suitable for the synthesis of Si/C composite anodes and provide insights for understanding the interaction between carbon and silicon during the charging/discharging process.
基金supported by National Natural Science Foundation of China(Nos.51875199 and 51905165)Hunan Natural Science Fund Project(2019JJ50186)the Key Research and Development Program of Hunan Province(No.2018GK2073).
文摘To ensure wind turbine(WT)safe operations and improve the utilization rate of wind energy,effective evaluation of the operation state of the pitch system is critical.Therefore,a new method was proposed to evaluate the operation state of the pitch system of WT based on fuzzy comprehensive evaluation.Firstly,based on SCADA data,the working state of the pitch system under rated power state and power state of WT were analyzed.Secondly,through the analysis of characteristic parameters and physical mechanism of the pitch system,the consistency principle of characteristic parameters,the stability principle of power under rated state,and the stability principle of blade angle underpowered state were obtained.Next,based on the aforementioned principles,the evaluation indexes were established,and the fuzzy comprehensive evaluation method was used to establish the operation state evaluation model of the pitch system under rated power state and under power state of the WT.Finally,an example was provided to verify the effectiveness of the method.The evaluation model established in this study can be used as a technical reference for the online monitoring of WT pitch systems to ensure the safe and stable operation of WTs.
文摘Squaring the circle is one of the oldest challenges in mathematical geometry. In 1882, it was proven that π was transcendental, and the task of squaring the circle was considered impossible. Demonstrating that squaring the circle was not possible took place before discovering quantum mechanics. The purpose of this paper is to show that it is actually possible to square the circle when taking into account the Heisenberg uncertainty principle. The conclusion is clear: it is possible to square the circle when taking into account the Heisenberg uncertainty principle.
基金supported by the National Natural Science Foundation of China(Grant No.42241143)the pre-research projects on Civil Aerospace Technologies(No.D020104)funded by the China National Space Administration.
文摘The pitch angle distributions of ions and electrons can be affected by various processes;thus,they can serve as an important indicator of the physical mechanisms driving the dynamics of space plasmas.From observations from the Mars Ion and Neutral Particle Analyzer onboard the Tianwen-1 orbiter,we calculated the pitch angle distributions of protons in the Martian induced magnetosphere by using information from the magnetohydrodynamically simulated magnetic field,and we statistically analyzed the spatial occurrence pattern of different types of pitch angle distributions.Even though no symmetrical features were seen in the dataset,we found the dominance of the field-aligned distribution type over the energy range from 188 to 6232 eV.Maps of the occurrence rate showed the preferential presence of a trapped-like distribution at the lower altitudes of the surveyed nightside region.Although our results are more or less restricted by the adopted magnetic field,they indicate the complexity of the near-Mars proton pitch angle distributions and infer the possibility of wave–particle interactions in the Martian induced magnetosphere.
基金Beijing Municipal Social Science Foundation(22GLC062)Research on service function renewal of Beijing subway station living circle driven by multiple big data.Beijing Municipal Education Commission Social Science Project(KM202010009002)Young YuYou Talents Training Plan of North China University of Technology.
文摘In the first-tier cities,subway has become an important carrier and life focus of people’s daily travel activities.By studying the distribution of POIs of public service facilities around Metro Line 10,using GIS to quantitatively analyze the surrounding formats of subway stations,discussing the functional attributes of subway stations,and discussing the distribution of urban functions from a new perspective,this paper provided guidance and advice for the construction of service facilities.
文摘This paper presents a graphical procedure for the squaring of a circle of any radius. This procedure, which is based on a novel application of the involute profile, when applied to a circle of arbitrary radius (using only an unmarked ruler and a compass), produced a square equal in area to the given circle, which is 50 cm<sup>2</sup>. This result was a clear demonstration that not only is the construction valid for the squaring of a circle of any radius, but it is also capable of achieving absolute results (independent of the number pi (π), in a finite number of steps), when carried out with precision.
基金“Research on Reading Teaching Mode of Business English Majors From the Perspective of Literature Circles”(Project No.:2021SCG112)Laboratory Opening Project in Quzhou University(Project No.KFXM201808).
文摘Business English reading teaching under the mode of“literature circles”focuses on cultivating students’autonomy in reading,group cooperation,and the exchange of ideas among group members.In this teaching mode,teachers are no longer the masters of the reading classroom,but the helpers,participants,and researchers in the process of students’reading.The reconstruction of teachers’role can promote the benign development of relationship not only between teachers and students,but also between students and students,inject new impetus and vitality into the classroom,and improve students’reading literacy.
文摘Background:Good adherence to post-operative exercise is crucial for long-term exercise intervention programs aimed at improving compliance,motivation for functional exercise,and quality of life among breast cancer patients.This study aims to evaluate the application effect of quality control circles on postoperative functional exercise compliance in breast neoplasm patients.Methods:A comprehensive search was conducted in CNKI,Wanfang,VIP,CBM,PubMed,Cochrane Library,Web of Science and CINAHL databases from their establishment to May 06,2023.Manual search and backtracking of relevant literature were also conducted.The search terms included a combination of subject terms and free words.Meta-analysis was performed using RevMan 5.4 software on eligible literature.Results:Initially,517 papers were retrieved,and after removing duplicates 238 papers using NoteExpress software,279 titles and abstracts were reviewed.Subsequently,225 non-compliant papers were excluded,leaving 54 full texts to be read.After excluding 38 non-compliant papers,16 eligible papers were included for Meta-analysis.These papers comprised a total of 1,342 patients(679 in the test group and 663 in the control group).The heterogeneity test using a fixed effects model showed P=0.22 and I2=21%.The Meta-analysis results demonstrated that the implementation of quality control circles alongside usual care significantly improved compliance with postoperative functional exercise in breast cancer patients(odds ratio=6.68,95%confidence interval(4.97,8.98),P<0.00001).Conclusion:Quality control circles activities can effectively enhance compliance with post-operative functional exercise among breast cancer patients,aiding in the recovery of affected limb function,improvement of self-care ability,and early reintegration into society and normal life,thereby enhancing quality of life.It is important to continually accumulate experience in applying relevant quality control circles activities in clinical work and promptly enhance the level of care accordingly,as the functional exercise of breast cancer patients after surgery involves a long-term and gradual improvement process.
