数据挖掘技术能够从大量、不完全、有噪声、模糊、随机的实际应用数据中,提取隐含在其中的、人们事先不知道的本质的规律。为了有效地发现旋转机械故障诊断过程中的故障征兆知识,引入数据挖掘技术和方法。针对旋转机械,构建了基于重复...数据挖掘技术能够从大量、不完全、有噪声、模糊、随机的实际应用数据中,提取隐含在其中的、人们事先不知道的本质的规律。为了有效地发现旋转机械故障诊断过程中的故障征兆知识,引入数据挖掘技术和方法。针对旋转机械,构建了基于重复增量修枝算法RIPPER(Repeated Incremental Pruning to Produce Error Reduction)的故障诊断知识获取系统。通过收集故障现象并整理成由故障征兆、故障类型等组成的故障信息样本,应用RIPPER算法对故障进行分析得到故障诊断规则集文件,实现故障诊断系统知识的获取和自动更新,并能对旋转机械的常见故障进行诊断,验证了算法的合理性。展开更多
No1 DVD Ripper是一个功能强大而且非常容易使用的DVD备份软件，使用本程序．你可以轻松的将DVD影片备份为VCD（MPEG1）或者SVCD格式(MPEG2），也可以转换为AVI或者DIVX（MPEG4)等多媒体文件格式，程序将DVD影片备份为相同视频质量的DIV...No1 DVD Ripper是一个功能强大而且非常容易使用的DVD备份软件，使用本程序．你可以轻松的将DVD影片备份为VCD（MPEG1）或者SVCD格式(MPEG2），也可以转换为AVI或者DIVX（MPEG4)等多媒体文件格式，程序将DVD影片备份为相同视频质量的DIVX文件而体积只有原来的10％，支持批量转换功能内置快捷属性设置面板，支持Skin面板更换技术，内置4套面板，非常容易使用。展开更多
During the last months of 1888 the populous quarter of Whitechapel, London, was stained with the blood of five women, all booked prostitutes and chronic alcoholics, worthy representatives of the diseases/vices of the ...During the last months of 1888 the populous quarter of Whitechapel, London, was stained with the blood of five women, all booked prostitutes and chronic alcoholics, worthy representatives of the diseases/vices of the Victorian East End. The shrewd and sanguinary Monster who realized these violent murders called himself ＂Jack the Ripper＂, signing with his ＂trade name＂ the letters he sent to the Central News Agency and through the press he soon became a myth, the most famous ＂serial killer＂ of all time. As a matter of fact, his legend survived, and his evil figure still haunts the pages of books and---of course--the frames of many films; among the most famous From Hell （2001） by Albert and Allen Hughes, taken from the graphic novel of the same name by Moore and Campbell; Jack the Ripper （1976） by Jess Franco, with a disturbing Klaus Kinski, but also the TV movie directed by David Wickes in 1998 entitled Jack The Ripper; more obliquely, Jack appears also in The Lodger （1913） and Frenzy （1972） by Alfred Hitchcock. But can these movies be defined as true biopics of Jack？ Strangely enough, it seems, these biographies contribute to build the mythic ＂anonymity＂ of the Ripper, encouraging （and fascinating） fear and nightmares.展开更多
To elucidate the wear mechanisms of the scraper in shield tunneling through sandy pebble strata,this study aims to achieve high efficiency and low wear during the tunneling process.We evaluate the operational paramete...To elucidate the wear mechanisms of the scraper in shield tunneling through sandy pebble strata,this study aims to achieve high efficiency and low wear during the tunneling process.We evaluate the operational parameters and tool wear characteristics of a 9-m diameter spoke-type shield machine used on the Beijing Daxing Airport Line.The analysis focuses on the wear values of the scrapers and rippers,wear of the scraper in different wear forms,and scraper wear relative to the position of the rippers obtained from the field.The study yielded the following conclusions.The wear values of scrapers on different spokes vary significantly owing to ripper protection.The wear of the scrapers can be categorized into six types:tooth chipping,local damage of teeth,wear of side teeth,wave-type of wear,wear on intermediate teeth,and flat wear,with the majority exhibiting wear on the side and intermediate teeth.The 0°spoke maintained the initial shape of the scrapers,making it more suitable for tunneling in sandy pebble strata.Based on the differences in the relative positions of the ripper and scraper,a model is proposed to determine the ripper plowing influence area.It was found that this area depends on the geological conditions of the soil;thus,the influence angle of ripper plowing in the considered sandy pebble strata is determined to be between 35°and 50°.The results obtained in this study provide a theoretical reference for optimizing scraper layouts in shield construction,even when operating under varying geological conditions.展开更多
Over the past decades,scientists have studied tillage and soil processing technologies based on the classical shapes of agricultural tools.Numerous studies highlight the importance of agricultural tool longevity in re...Over the past decades,scientists have studied tillage and soil processing technologies based on the classical shapes of agricultural tools.Numerous studies highlight the importance of agricultural tool longevity in relation to abrasive wear resistance and draught force values.However,these studies are typically limited to the most common shapes and types of tools.This paper combines the insights gained from the marine industry's experience in the design of ship's bulbous bows with the challenges of designing soil rippers for agricultural machinery.New shape elements were developed based on the delta,oval,and nabla types of bulbous bows used in ships.Thirteen types of designed elements,along with the original shape,were tested virtually using the Discrete Element Method(DEM).The 3D-printed samples were then tested in a sand bin to measure draught force.DEM simulation parameters were validated by measuring the Static Angle of Repose(SAOR)of sand.The results of this study demonstrate that applying a bulbous bow-inspired shape to the soil ripper can reduce draught force by 7.1%;however,in some cases,it can also increase the force by 4.1%compared to the original shape.The values are giving statistically significant differences between the experimental measurements.To fully evaluate the application of these designed elements,further soil disturbance and wear analysis studies should be conducted in future research.展开更多
基金国家自然科学基金(the National Natural Science Foundation of China under Grant No.50375017)北京市自然科学基金(the Natural Science Foundation of Beijing City of China under Grant No.3042006+1 种基金No.3062008)机电系统测控北京市重点实验室开放课题资助 (No.KF20041123206)
文摘数据挖掘技术能够从大量、不完全、有噪声、模糊、随机的实际应用数据中,提取隐含在其中的、人们事先不知道的本质的规律。为了有效地发现旋转机械故障诊断过程中的故障征兆知识,引入数据挖掘技术和方法。针对旋转机械,构建了基于重复增量修枝算法RIPPER(Repeated Incremental Pruning to Produce Error Reduction)的故障诊断知识获取系统。通过收集故障现象并整理成由故障征兆、故障类型等组成的故障信息样本,应用RIPPER算法对故障进行分析得到故障诊断规则集文件,实现故障诊断系统知识的获取和自动更新,并能对旋转机械的常见故障进行诊断,验证了算法的合理性。
文摘No1 DVD Ripper是一个功能强大而且非常容易使用的DVD备份软件，使用本程序．你可以轻松的将DVD影片备份为VCD（MPEG1）或者SVCD格式(MPEG2），也可以转换为AVI或者DIVX（MPEG4)等多媒体文件格式，程序将DVD影片备份为相同视频质量的DIVX文件而体积只有原来的10％，支持批量转换功能内置快捷属性设置面板，支持Skin面板更换技术，内置4套面板，非常容易使用。
文摘During the last months of 1888 the populous quarter of Whitechapel, London, was stained with the blood of five women, all booked prostitutes and chronic alcoholics, worthy representatives of the diseases/vices of the Victorian East End. The shrewd and sanguinary Monster who realized these violent murders called himself ＂Jack the Ripper＂, signing with his ＂trade name＂ the letters he sent to the Central News Agency and through the press he soon became a myth, the most famous ＂serial killer＂ of all time. As a matter of fact, his legend survived, and his evil figure still haunts the pages of books and---of course--the frames of many films; among the most famous From Hell （2001） by Albert and Allen Hughes, taken from the graphic novel of the same name by Moore and Campbell; Jack the Ripper （1976） by Jess Franco, with a disturbing Klaus Kinski, but also the TV movie directed by David Wickes in 1998 entitled Jack The Ripper; more obliquely, Jack appears also in The Lodger （1913） and Frenzy （1972） by Alfred Hitchcock. But can these movies be defined as true biopics of Jack？ Strangely enough, it seems, these biographies contribute to build the mythic ＂anonymity＂ of the Ripper, encouraging （and fascinating） fear and nightmares.
基金Supported by Beijing Municipal Natural Science Foundation of China(Grant No.8252017)National Natural Science Foundation of China(Grant Nos.51608521,52178375)Beijing Urban Construction Group Co.,Ltd.
文摘To elucidate the wear mechanisms of the scraper in shield tunneling through sandy pebble strata,this study aims to achieve high efficiency and low wear during the tunneling process.We evaluate the operational parameters and tool wear characteristics of a 9-m diameter spoke-type shield machine used on the Beijing Daxing Airport Line.The analysis focuses on the wear values of the scrapers and rippers,wear of the scraper in different wear forms,and scraper wear relative to the position of the rippers obtained from the field.The study yielded the following conclusions.The wear values of scrapers on different spokes vary significantly owing to ripper protection.The wear of the scrapers can be categorized into six types:tooth chipping,local damage of teeth,wear of side teeth,wave-type of wear,wear on intermediate teeth,and flat wear,with the majority exhibiting wear on the side and intermediate teeth.The 0°spoke maintained the initial shape of the scrapers,making it more suitable for tunneling in sandy pebble strata.Based on the differences in the relative positions of the ripper and scraper,a model is proposed to determine the ripper plowing influence area.It was found that this area depends on the geological conditions of the soil;thus,the influence angle of ripper plowing in the considered sandy pebble strata is determined to be between 35°and 50°.The results obtained in this study provide a theoretical reference for optimizing scraper layouts in shield construction,even when operating under varying geological conditions.
基金This project has received funding from the Research Council of Lithuania(LMTLT),agreement No S-PD-24-31.
文摘Over the past decades,scientists have studied tillage and soil processing technologies based on the classical shapes of agricultural tools.Numerous studies highlight the importance of agricultural tool longevity in relation to abrasive wear resistance and draught force values.However,these studies are typically limited to the most common shapes and types of tools.This paper combines the insights gained from the marine industry's experience in the design of ship's bulbous bows with the challenges of designing soil rippers for agricultural machinery.New shape elements were developed based on the delta,oval,and nabla types of bulbous bows used in ships.Thirteen types of designed elements,along with the original shape,were tested virtually using the Discrete Element Method(DEM).The 3D-printed samples were then tested in a sand bin to measure draught force.DEM simulation parameters were validated by measuring the Static Angle of Repose(SAOR)of sand.The results of this study demonstrate that applying a bulbous bow-inspired shape to the soil ripper can reduce draught force by 7.1%;however,in some cases,it can also increase the force by 4.1%compared to the original shape.The values are giving statistically significant differences between the experimental measurements.To fully evaluate the application of these designed elements,further soil disturbance and wear analysis studies should be conducted in future research.
