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Stereoselective construction of azepine-containing bridged scaffolds via organocata-lytic bicyclization of yne-allenone esters with nitrones
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作者 Meng-Fan Li Shao-Qing Shi +6 位作者 Ting Xu Qian Zhang Wen-Juan Hao Shu-Liang Wang Jianyi Wang Shu-Jiang Tu Bo Jiang 《Chinese Chemical Letters》 SCIE CAS CSCD 2023年第4期309-312,共4页
A new organocatalytic double annulation cascade involving scission/recombination of N-O bonds of nitrones is reported for the first time, and used to produce a range of hitherto unprecedented tricyclic bridged-fused b... A new organocatalytic double annulation cascade involving scission/recombination of N-O bonds of nitrones is reported for the first time, and used to produce a range of hitherto unprecedented tricyclic bridged-fused benzo[d]azepines bearing three stereogenic centers with moderate to good yields and complete diastereoselectivity. A quinine-catalyzed reaction of yne–allenone esters with nitrones worked well and provided a convergent and regioselective pathway to access these three-dimensional scaffolds from the planar conjugated system. Density functional theory(DFT) calculations have been applied to understand the key process for forming diradical intermediates. 展开更多
关键词 bicyclization DIASTEREOSELECTIVITY Organocatalysis Bridged heterocycles YNE-allenone esters NITRONES
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Improved YOLOv8n Model for Detecting Helmets and License Plates on Electric Bicycles 被引量:1
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作者 Qunyue Mu Qiancheng Yu +2 位作者 Chengchen Zhou Lei Liu Xulong Yu 《Computers, Materials & Continua》 SCIE EI 2024年第7期449-466,共18页
Wearing helmetswhile riding electric bicycles can significantly reduce head injuries resulting fromtraffic accidents.To effectively monitor compliance,the utilization of target detection algorithms through traffic cam... Wearing helmetswhile riding electric bicycles can significantly reduce head injuries resulting fromtraffic accidents.To effectively monitor compliance,the utilization of target detection algorithms through traffic cameras plays a vital role in identifying helmet usage by electric bicycle riders and recognizing license plates on electric bicycles.However,manual enforcement by traffic police is time-consuming and labor-intensive.Traditional methods face challenges in accurately identifying small targets such as helmets and license plates using deep learning techniques.This paper proposes an enhanced model for detecting helmets and license plates on electric bicycles,addressing these challenges.The proposedmodel improves uponYOLOv8n by deepening the network structure,incorporating weighted connections,and introducing lightweight convolutional modules.These modifications aim to enhance the precision of small target recognition while reducing the model’s parameters,making it suitable for deployment on low-performance devices in real traffic scenarios.Experimental results demonstrate that the model achieves an mAP@0.5 of 91.8%,showing an 11.5%improvement over the baselinemodel,with a 16.2%reduction in parameters.Additionally,themodel achieves a frames per second(FPS)rate of 58,meeting the accuracy and speed requirements for detection in actual traffic scenarios. 展开更多
关键词 YOLOv8 object detection electric bicycle helmet detection electric bicycle license plate detection
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Understanding the combustion behavior of electric bicycle batteries and unveiling its relationship with fire extinguishing
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作者 Zhanglong Yu Xueling Shen +6 位作者 Ran Xu Zheng Wang Zengming Wan Mingyang Chen Yi Cui Yanyan Fang Xiaoli Ma 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2024年第4期609-618,共10页
In this study,a detailed analysis of the combustion behaviors of the lithium iron phosphate(LFP)and lithium manganese oxide(LMO)batteries used in electric bicycles was conducted.This research included quantitative mea... In this study,a detailed analysis of the combustion behaviors of the lithium iron phosphate(LFP)and lithium manganese oxide(LMO)batteries used in electric bicycles was conducted.This research included quantitative measurements of the combustion duration,flame height,combustion temperature,heat release rate,and total heat release.The results indicated that LMO batteries exhibited higher combustion temperatures of 600–700°C,flame heights of 70–75 cm,a significantly higher heat release rate of40.1 k W(12 Ah),and a total heat release of 1.04 MJ(12 Ah)compared to LFP batteries with the same capacity.Based on these experimental results,a normalized total heat release(NORTHR)parameter was proposed,demonstrating good universality for batteries with different capacities.Utilizing this parameter,quantitative calculations and optimization of the extinguishing agent dosage were conducted for fires involving these two types of batteries,and the method was validated by extinguishing fires for these two types of battery packs with water-based extinguishing fluids. 展开更多
关键词 Combustion behavior Electric bicycle Lithium-ion battery Fire extinguishing Normalized total heat release
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Knowledge, Attitude, and Practice of Using Helmets in Children amongst Parents to Prevent Head Injuries: A Cross-Sectional Study in Riyadh, Saudi Arabia
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作者 Turki Salah Aldeen Bukhari Abdullah Yahya Aldhban +4 位作者 Anas Abdulrahman Alqasem Dona Jamal Al Hatlani Hareth Aldosaimani Hamad A. Al Madi Khalid Alqahtani 《Open Journal of Pediatrics》 2024年第2期255-265,共11页
Objectives: The primary objective was to characterize the range of Knowledge, Attitude, and Practice (KAP) of Helmet use in children amongst parents to prevent head injuries and death. Methods: This is a cross-section... Objectives: The primary objective was to characterize the range of Knowledge, Attitude, and Practice (KAP) of Helmet use in children amongst parents to prevent head injuries and death. Methods: This is a cross-sectional study, done by online survey using a snowball sampling technique, the number of included responses were 386 parents (Male and female) living in Riyadh Aged 21 - 60 years old or above. Results: The study showed that there is a difference in Parents’ belief in the importance of helmet use while riding a Bicycle vs Motorcycle/Quad bike and that was affected by parents’ education level, almost all the people who answered the survey (76.7%) agree that it is important for their children to wear a helmet when riding both a Bicycle and a Motorcycle or Quadbike with a cumulative percentage of (93.8%). And almost all agreed on multiple approaches to help increase helmet use be it by forcing rental shops to give out helmets, forcing sellers to recommend the use of helmets, increasing awareness campaigns, and imposing fines for not wearing helmets. Conclusions: This study is the first to explore Family helmet use while riding Bicycles and Motorcycles/Quad bikes. Although Parent’s belief in the importance of helmet use for their children was high, it is clear that the level of practice is low. With that the risk of head injuries might be high, our findings suggest that safety interventions for increasing pediatric helmet use are needed to increase helmet use and reduce the risk of head injury and hospitalization. 展开更多
关键词 Head Trauma Head Injury Helmet Bicycle Motorcycle Quad Bike KAP Knowledge ATTITUDE PRACTICE
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Research on Planning and Design of Multi-Story Prefabricated Electric Bicycle Charging Parking Lot in Urban and Rural Areas
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作者 Liya Fang 《Journal of Architectural Research and Development》 2024年第4期77-91,共15页
In recent years,disorderly parking and difficult charging of electric bicycles have been challenges in urban management.The rapid growth of electric bicycles is in contradiction with the lack of dedicated parking spac... In recent years,disorderly parking and difficult charging of electric bicycles have been challenges in urban management.The rapid growth of electric bicycles is in contradiction with the lack of dedicated parking spaces and charging service facilities in towns and villages.To solve the issue of parking and charging electric bicycles in limited urban and rural spaces,prefabricated building technology is applied to the design of a multi-story electric bicycle parking lot.The multi-story prefabricated electric bicycle parking lot is utilized in urban and rural planning and design to upgrade parking facilities in old urban areas,land-constrained commercial areas,as well as counties,towns,and rural areas with inadequate municipal facilities.Multi-story prefabricated electric bicycle parking lots are the application exploration of industrial buildings,and promote the high-quality development planning and construction of towns and counties and villages.Compared with the single-story metal charging station,the multi-story assembled electric bicycle parking lot has the characteristics of integrating parking and charging,being more durable and safer in structure,accommodating a large number of vehicles,and improving the space utilization rate. 展开更多
关键词 Prefabricated building Electric bicycle Parking lot
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Student Bicycle Sharing System in Zagreb-Studocikl
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作者 LjupkoŠimunović 《Journal of Traffic and Transportation Engineering》 2024年第6期299-304,共6页
The system of public bicycles in the world known as"Bicycle sharing",is a service in which bicycles are made available for shared use to individuals with or without a certain fee.Users can take and return th... The system of public bicycles in the world known as"Bicycle sharing",is a service in which bicycles are made available for shared use to individuals with or without a certain fee.Users can take and return the bike at numerous locations in the urban parts of the city.As part of the CIVITAS ELAN project(2008-2012),which was aimed at improving the quality of life of citizens by establishing high-quality solutions in city traffic and to promote and encourage sustainable,clean and energy-efficient modes of traffic,a pilot project of student public bicycle(Studocikl)was implemented at the University of Zagreb.In the first phase the pilot project included the Faculty of Transport and Traffic Sciences(FTTS)where is currently implemented.In the second phase the project is planned to include the remaining faculties located at the Borongaj Campus.The idea behind the Studocikl project is to connect two remote locations of FTTS,between headquarters in Vukelićeva Street and Borongaj Campus.Registration(login,logout)of users and the entire administration is done through a web portal.Time of using bicycles is in the period from 8 am to 8 pm(working hours of FTTS).Studocikl was officially put into operation on the 17 September 2012 and in this paper will analyse its one-year operation.The paper will also make proposals for further Studocikl development in terms of:installing GPS trackers for satellite bicycle tracking,the application for smartphones,full automation of the registration,and explore the possibility of extending such service and modes of transportation at all faculties in the University of Zagreb. 展开更多
关键词 Sustainable urban mobility non-motorised transport bicycle sharing system
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Is It about a Bicycle? A Posthumanist Perspective on the Role of Women’s Bicycles in WWII Resistance Movements
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作者 Zuzana Križalkovičová 《Sociology Study》 2024年第4期198-211,共14页
Drawing upon Donna Haraway’s cyborg theory,this paper argues that the bicycle can be conceived as a cyborg extension of body and identity which transcended its mechanical essence to become an integral co-partner for ... Drawing upon Donna Haraway’s cyborg theory,this paper argues that the bicycle can be conceived as a cyborg extension of body and identity which transcended its mechanical essence to become an integral co-partner for women involved in resistance activities in WWII.More specifically,the study explores how women used cycling during World War Ⅱ not only for mobility but as a profound expression of courage,endurance and solidarity which enabled them to overcome physical and symbolic barriers under totalitarian regimes.The bicycle emerges not only as a central co-agent but also actively co-creates the situations in which it emerges as a transformative force.Cycling acted as a catalyst for personal and collective empowerment,fostering new subjectivities while transcending physical and social limitations.This study sparks multidimensional discourse on how technological tools can co-create our societies and identities,offering insights into how bicycles can drive socio-political change,promote emancipation and foster inclusivity. 展开更多
关键词 BICYCLE female involvement in World WarⅡresistance movements cyborg theory
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路面机动目标的融合跟踪 被引量:2
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作者 陈莹 韩崇昭 《仪器仪表学报》 EI CAS CSCD 北大核心 2004年第z1期593-594,共2页
针对自主车辆的机动目标跟踪问题提出了一个利用雷达和图像传感器的融合跟踪方法。采用动力学模型对车辆运动进行描述以适应车辆机动的情形。利用雷达的距离信息建立视觉窗口,利用三维线框模型从窗口图像中获取车辆转向角,然后通过数据... 针对自主车辆的机动目标跟踪问题提出了一个利用雷达和图像传感器的融合跟踪方法。采用动力学模型对车辆运动进行描述以适应车辆机动的情形。利用雷达的距离信息建立视觉窗口,利用三维线框模型从窗口图像中获取车辆转向角,然后通过数据融合技术,充分利用雷达与图像传感的量测信息,提高对机动目标的状态估计精度。三维仿真实验证明,与单纯基于雷达量测的跟踪方法相比,该融合方法大大提高了对机动目标的跟踪精度。 展开更多
关键词 Bicycle模型 目标跟踪 视觉窗口 线框模型 信息融合
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Concise synthesis of oxy-bridged bicyclic azasugar and thiosugar as potential glycosidase inhibitors
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作者 孟祥豹 李妍萍 李中军 《Journal of Chinese Pharmaceutical Sciences》 CAS 2007年第1期43-46,共4页
Aim To develop a concise method for the synthesis of bicyclic azasugar and thiosugar with novel scaffold. Methods The two primary hydroxyl groups of compound 1 were selectively protected with tosyl cloloride in pyridi... Aim To develop a concise method for the synthesis of bicyclic azasugar and thiosugar with novel scaffold. Methods The two primary hydroxyl groups of compound 1 were selectively protected with tosyl cloloride in pyridine, followed by ring-closure with sodium sulfide or primary amine to form the oxy-bridged bicyclic molecules in good yields. Results Two bicyclic azasugars and a thiosugar were produced from L-sorbose in several steps. Conclusion The described procedures provide an efficient method to synthesize bicyclic azasugar and thiosugar with novel scaffold as potential glycosidase inhibitors. 展开更多
关键词 Oxy-bridge Bicyclic azasugar Bicyclic thiosugar RING-CLOSURE
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Synthesis,Crystal Structure and Fluorescence of a Bicyclic Product Containing Chromene and Propargylamine Skeleton 被引量:1
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作者 庞韬 王慧 +3 位作者 吴雪 武琳 赵智勇 吴根华 《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 2016年第8期1277-1282,共6页
The bicyclic product containing a chromene skeleton and a propargylamine skeleton(C(22)H(22)N2O2) was synthesized from the double sites of terminal alkyne, piperazine derivative and formaldehyde via one-pot proc... The bicyclic product containing a chromene skeleton and a propargylamine skeleton(C(22)H(22)N2O2) was synthesized from the double sites of terminal alkyne, piperazine derivative and formaldehyde via one-pot procedure. Its structure was characterized by ^1H NMR, ^13C NMR, IR and H RMS, and further confirmed by single-crystal X-ray diffraction. It crystallizes in the monoclinic system, space group P21/n with a = 12.6571(14), b = 11.3249(12), c = 12.6571(14) A, β = 105.22°,V = 1750.6(3) A^3, Z = 4, R = 0.0568 and w R = 0.1444. The fluorescence of the product was discussed. 展开更多
关键词 crystallography fluorescence bicyclization chromene skeleton propargylamine skeleton
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走近微媒体体验营销——基于滴滴打车和ofo bicycle的案例研究 被引量:4
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作者 王倩 《企业研究》 2016年第7期40-43,共4页
随着移动APP的普及和电子商务的快速发展,移动支付市场的发展受到商家和消费者越来越多的关注和青睐。作为目前最前卫的支付工具,微信支付在体验式营销上有着得天独厚的优势。微信支付的同时,不仅给消费者带来了愉悦、便捷的消费体验,... 随着移动APP的普及和电子商务的快速发展,移动支付市场的发展受到商家和消费者越来越多的关注和青睐。作为目前最前卫的支付工具,微信支付在体验式营销上有着得天独厚的优势。微信支付的同时,不仅给消费者带来了愉悦、便捷的消费体验,同时也提升了企业的形象和实力。本文以"滴滴打车"和"ofo bicycle"为研究对象,运用规范的案例研究方法,以施密特体验营销的五要素模块为理论基础,分析微信的体验式营销是如何达到用户满意,实现成功营销的,并尝试构建微媒体体验营销下用户体验过程模型,为网络体验营销的发展和运用提供借鉴和参考。 展开更多
关键词 微媒体 ofo BICYCLE 体验式营销 运用规范 案例研究方法 移动支付 用户体验 支付工具 成功营销 网络体验
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Relationship between number of passing events and operating parameters in mixed bicycle traffic 被引量:2
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作者 闫星臣 何鹏 +2 位作者 陈峻 叶晓飞 刘擎超 《Journal of Southeast University(English Edition)》 EI CAS 2015年第3期418-423,共6页
This paper investigates the passing events between electric bicycles and conventional bicycles and explores the relationships between passing events and traffic parameters in bicycle facilities.Three exclusive bicycle... This paper investigates the passing events between electric bicycles and conventional bicycles and explores the relationships between passing events and traffic parameters in bicycle facilities.Three exclusive bicycle paths in Nanjing, China,were observed with cameras.Then,the field data including vehicle number,velocity characteristics and passing event features were analyzed in detail.Data analysis and fitting reveal that the speed difference has little impact on the passing event number,as does the bicycle ratio.The Gaussian function can better describe the relationship between the passing event number and bicycle volume (density).The valid use level of bicycle path width influences the inflexion of the passing events-density fitting curve.The conclusions can be applied for estimating the passing events in mixed bicycle flows and for choosing a suitable width of separate bicycle path. 展开更多
关键词 mixed bicycle traffic passing events traffic operating parameters correlation analysis
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Synthesis and Structure of A Novel Caged Bicyclic Phosphate Flame Retardant 被引量:28
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作者 Li, X Ou, YX +1 位作者 Zhang, YH Lian, DJ 《Chinese Chemical Letters》 SCIE CAS CSCD 2000年第10期887-890,共4页
PI novel caged bicyclic phosphate flame retardant tri(1-oxo-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane-methyl) phosphate (Trimer) was synthesized from 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octa... PI novel caged bicyclic phosphate flame retardant tri(1-oxo-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane-methyl) phosphate (Trimer) was synthesized from 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane (PEPA) and phosphorus oxychloride in this paper. Its structure was characterized by elemental analysis. FTIR, H-1 NMR. P-31 NMR and X-ray diffraction analysis. 展开更多
关键词 caged bicyclic phosphate flame retardant crystal structure
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Travel Behaviours of Sharing Bicycles in the Central Urban Area Based on Geographically Weighted Regression: The Case of Guangzhou, China 被引量:7
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作者 WEI Zongcai ZHEN Feng +3 位作者 MO Haitong WEI Shuqing PENG Danli ZHANG Yuling 《Chinese Geographical Science》 SCIE CSCD 2021年第1期54-69,共16页
Mobile information and communication technologies(MICTs) have fully penetrated everyday life in smart societies;this has greatly compressed time, space, and distance, and consequently, reshaped residents’ travel beha... Mobile information and communication technologies(MICTs) have fully penetrated everyday life in smart societies;this has greatly compressed time, space, and distance, and consequently, reshaped residents’ travel behaviour patterns. As a new mode of shared mobility, the sharing bicycle offers a variety of options for the daily travel of urban residents. Extant studies have mainly examined the travel characteristics and influencing factors of public bicycles with piles, while the travel patterns for sharing bicycles and their driving mechanisms have been largely ignored. Using one week’s travel data for Mobike, this study investigated the spatial and temporal distribution patterns of sharing bicycle travel behaviours in the central urban area of Guangzhou, China;furthermore, it identified the influences of built environment density factors on sharing bicycle travel behaviours based on the geographically weighted regression method. Obvious morning and evening peaks were observed in the sharing bicycle travel patterns for both weekdays and weekends. The old urban area, which had a high degree of mixed function, dense road networks, and cycling-friendly built environments, was the main travel area that attracted sharing bicycles on both weekdays and weekends. Furthermore, factors including the point of interest(POI) for the density of public transport stations, the functional mixing degree, and the density of residential POIs significantly affected residents’ travel behaviours. These findings could enrich discourse regarding shared mobility with a Chinese case characterised by rapidly developing MICTs and also provide references to local authorities for improving slow traffic environments. 展开更多
关键词 sharing bicycles travel behaviours smart societies geographically weighted regression analysis Guangzhou China
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Mixed traffic flow modeling near Chinese bus stops and its applications 被引量:5
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作者 杨小宝 四兵锋 环梅 《Journal of Central South University》 SCIE EI CAS 2012年第9期2697-2704,共8页
To determine how bus stop design influences mixed traffic operation near Chinese bus stops,a new theoretical method was developed by using additive-conflict-flows procedure.The procedure was extended from homogeneous ... To determine how bus stop design influences mixed traffic operation near Chinese bus stops,a new theoretical method was developed by using additive-conflict-flows procedure.The procedure was extended from homogeneous traffic flow to mixed traffic flow.Based on the procedure and queuing theory,car capacity and speed models were proposed for three types of bus stops including curbside,bus bay and bicycle detour.The effects of various combinations of bus stop type,traffic volume,bus dwell time,and berth number on traffic operations were investigated.The results indicate that traffic volume,bus dwell time and berth number have negative effects on traffic operations for any type of bus stops.For different types of bus stops,at car volumes above approximately 200 vehicles per hour,the bus bay and bicycle detour designs provide more benefits than the curbside design.As traffic volume increases,the benefit firstly increases in uncongested conditions and then decreases in congested conditions.It reaches the maximum at car volumes nearly 1 100 vehicles per hour.The results can be used to aid in the selection of a preferred bus stop design for a given traffic volume in developing countries. 展开更多
关键词 mixed traffic flow bus stop road capacity SPEED bicycles
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Evolution and organic geochemical significance of bicyclic sesquiterpanes in pyrolysis simulation experiments on immature organic-rich mudstone 被引量:3
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作者 Gang Yan Yao-Hui Xu +2 位作者 Yan Liu Peng-Hai Tang Wei-Bin Liu 《Petroleum Science》 SCIE CAS CSCD 2019年第3期502-512,共11页
Sesquiterpanes are ubiquitous components of crude oils and ancient sediments.Liquid saturated hydrocarbons from simulated pyrolysis experiments on immature organic-rich mudstone collected from the Lower Cretaceous Hes... Sesquiterpanes are ubiquitous components of crude oils and ancient sediments.Liquid saturated hydrocarbons from simulated pyrolysis experiments on immature organic-rich mudstone collected from the Lower Cretaceous Hesigewula Sag were analyzed by gas chromatography-mass spectrometry(GC-MS).C14 bicyclic sesquiterpanes,namely,8β(H)-drimane,8β(H)-homodrimane,and 8 a(H)-homodrimane were detected and identified on basis of their diagnostic fragment ions(m/z123,179,193,and 207),and previously published mass spectra data,and these bicyclic sesquiterpanes presented relatively regular characteristics in their thermal evolution.The ratios 8β(H)-drimane/8β(H)-homodrimane,8β(H)-homodrimane/8 a(H)-homodrimane,and 8β(H)-drimane/8 a(H)-homodrimane all show a clear upward trend with increasing temperature below the temperature turning point.Thus,all these ratios can be used as evolution indexes of source rocks in the immature-lowmaturity stage.However,the last two ratios may be more suitable than the first ratio as valid parameters for measuring the extent of thermal evolution of organic matter in the immature-low-maturity stage because their change amplitude with increasing temperature is more obvious. 展开更多
关键词 Immature-low-maturity stage Simulated PYROLYSIS experiment BICYCLIC sesquiterpanes Thermal EVOLUTION MATURITY indicators
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Analysis and Comparison of Safety and Fatigue Comfort of Postal Bicycles Based on Finite Element Method and sEMG 被引量:5
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作者 项忠霞 李亚南 +1 位作者 田冠 常振元 《Transactions of Tianjin University》 EI CAS 2013年第4期272-278,共7页
The safety and the fatigue comfort were compared between a domestic and a Japanese postal bicycle. Firstly, the fatigue comfort of these two kinds of bicycles was evaluated by surface electromyographic signal (sEMG) e... The safety and the fatigue comfort were compared between a domestic and a Japanese postal bicycle. Firstly, the fatigue comfort of these two kinds of bicycles was evaluated by surface electromyographic signal (sEMG) experiment, in which human lower limb muscle groups were research objects, and the average EMG (AEMG) index and median frequency (MF) were chosen as the evaluation indexes. Secondly, the safety of these two kinds of bicycle frames was analyzed and compared by using the finite element analysis. The results show that the riding fatigue comfort of the Japanese postal bicycle is better, and the Japanese postal bicycle frame is more safe and reasonable although both the postal bicycles meet the requirement for strength. Finally, based on the above analysis, the frame structure and related parameters of the domestic postal bicycle were improved with reference to the Japanese postal bicycle and biomechanics theory. 展开更多
关键词 postal bicycle surface electromyogram signal evaluation index fatigue comfort finite element analysis
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The atom-bond connectivity index of chemical bicyclic graphs 被引量:4
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作者 CHEN Jin-song GUO Xiao-feng 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2012年第2期243-252,共10页
The atom-bond connectivity(ABC) index provides a good model for the stability of linear and branched alkanes as well as the strain energy of cycloalkanes,which is defined as ABC(G) =∑ uv∈E(G) √d u+dv-2 dudv,... The atom-bond connectivity(ABC) index provides a good model for the stability of linear and branched alkanes as well as the strain energy of cycloalkanes,which is defined as ABC(G) =∑ uv∈E(G) √d u+dv-2 dudv,where du denotes the degree of a vertex u in G.A chemical graph is a graph in which no vertex has degree greater than 4.In this paper,we obtain the sharp upper and lower bounds on ABC index of chemical bicyclic graphs. 展开更多
关键词 atom-bond connectivity index chemical bicyclic graph bound.
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Optimal Design of Bicycle Frame Parameters Considering Biomechanics 被引量:3
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作者 XIANG Zhongxia XU Ruifen +1 位作者 BU Yan WU Xiaofan 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2011年第1期141-145,共5页
With the development of technology and the change of market demands,the trend in middle and high grade bicycle manufacturing is developed toward small-volume,multi-species,and customer-oriented production.Therefore,hu... With the development of technology and the change of market demands,the trend in middle and high grade bicycle manufacturing is developed toward small-volume,multi-species,and customer-oriented production.Therefore,human element should be fully considered in design so that the bicycle has the best cycling performance for the specific rider.Currently,customized design is difficult to achieve since feature parameters of the rider are not included in the design.The design of bicycle frame is the most important in bicycle design.The relative positions among the saddle,handlebar and central axis are defined as the bicycle three-pivot,they are the main parameters in bicycle frame design.In conventional bicycle design,frame parameters are merely relevant to bicycle types.On the basis of the principles of biomechanics and ergonomics knowledge,this paper presents a design method for bicycle three-pivot considering feature parameters of the rider by dynamic simulation.Firstly,a dynamic model of rider-bicycle system is built for a special rider,and a serial of simulation experiments is designed by uniform test method.Then,a mathematical model is built between the three-pivot position and the square of lower limb muscle stress by using simulation and regression analysis of the rider-bicycle system.The optimal three-pivot position parameters are obtained by setting the minimal of the square of the lower limb muscle stress as the objective.Therefore,the optimal parameters are gained for the specific rider.Finally,various results are gained for different riders based on the same design process.The function between feature parameters of the rider and the optimum three-pivot position parameters is built by regression.Bicycle design considering biomechanics can be divided into three main steps:calculating the three-pivot position,designing the geometrical structure of the bicycle frame and analyzing frame strength,and selecting appropriate parts and assembling the bicycle.Bicycle design considering biomechanics changes the conventional bicycle design and realizes customized design by considering human element in the design process. 展开更多
关键词 bicycle design BIOMECHANICS muscle fatigue feature parameters of the rider
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Theoretical Studies on the Thermodynamic Properties and Detonation Performances of Bicyclic Nitramines:TNAD Isomers 被引量:3
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作者 QIU Ling XIAO He-Ming GONG Xue-Dong JU Xue-Hai 《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 北大核心 2006年第11期1309-1320,共12页
Ab initio molecular orbital calculations have been performed at Hartree-Fock (HF), second-order Mrller-Plesset (MP2), and hybrid density functional theory (DFT) B3LYP levels with 6-31G^** basis set to investig... Ab initio molecular orbital calculations have been performed at Hartree-Fock (HF), second-order Mrller-Plesset (MP2), and hybrid density functional theory (DFT) B3LYP levels with 6-31G^** basis set to investigate the low sensitive explosive trans-1,4,5,8-tetranitro-1,4,5,8- tetraazadecalin (TNAD) and its seven bicyclic isomers. Their molecular geometries, electronic structures, thermodynamic properties, and detonation performances were predicted and compared. The relationships between structures and various properties were discussed in detail. The calculated results agree well with the available experimental data, and suggest that some compounds may be novel potential candidates of high energy density materials (HEDMs) with performances better than TNT (2,4,6-trinitrotoluene) and similar to RDX (1,3,5-trinitro-1,3,5-triazacyclohexane). 展开更多
关键词 bicyclic nitramine Hartree-Fock method MP2 method density functional theory thermodynamic properties detonation performances
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