详细论述了有限元的基本理论,根据实际情况,考虑船舶推进轴系校中计算中剪切变形的影响,对有限元法的刚度矩阵进行了改进。利用V B.N ET 开发了船舶推进轴系校中计算通用软件,通过与没有考虑剪切变形的国内外同类计算软件计算结果的比...详细论述了有限元的基本理论,根据实际情况,考虑船舶推进轴系校中计算中剪切变形的影响,对有限元法的刚度矩阵进行了改进。利用V B.N ET 开发了船舶推进轴系校中计算通用软件,通过与没有考虑剪切变形的国内外同类计算软件计算结果的比较以及实际中的应用,表明了这种改进是合理的且可以获得更准确的结果。所开发的计算软件,界面友好,功能完善,操作简单,满足轴系设计计算、校核计算的需要,进一步完善了船舶推进轴系校中计算模型,便于二次开发与深入研究。展开更多
Shaft alignment is an important technique during installation and maintenance of a rotating machine. A high-precision laser alignment system has been designed with dual PSDs (Position Sensing Detector) to change tradi...Shaft alignment is an important technique during installation and maintenance of a rotating machine. A high-precision laser alignment system has been designed with dual PSDs (Position Sensing Detector) to change traditional manual way of shaft alignment and to make the measurement easier and more accurate. The system is comprised of two small measuring units (laser transmitter and detector) and a PDA (Personal Digital Assistant) with measurement software. The laser alignment system with dual PSDs was improved on a single PSD system, and yields higher measurement accuracy than the previous design, and has been successful for designing and implements actual shaft alignment. In the system, the range of offset measurement is ±4 mm, and the resolution is 1.5 μm, with accuracy being less than 2 μm.展开更多
Knee osteoarthritis(OA) is a progressive joint disease hallmarked by cartilage and bone breakdown and associated with changes to all of the tissues in the joint,ultimately causing pain,stiffness,deformity and disabili...Knee osteoarthritis(OA) is a progressive joint disease hallmarked by cartilage and bone breakdown and associated with changes to all of the tissues in the joint,ultimately causing pain,stiffness,deformity and disability in many people.Radiographs are commonly used for the clinical assessment of knee OA incidence and progression,and to assess for risk factors.One risk factor for the incidence and progression of knee OA is malalignment of the lower extremities(LE).The hipknee-ankle(HKA) angle,assessed from a full-length LE radiograph,is ideally used to assess LE alignment.Careful attention to LE positioning is necessary to obtain the most accurate measurement of the HKA angle.Since full-length LE radiographs are not always available,the femoral shaft-tibial shaft(FS-TS) angle may be calculated from a knee radiograph instead.However,the FS-TS angle is more variable than the HKA angle and it should be used with caution.Knee radiographs are used to assess the severity of knee OA and its progression.There are three types of ordinal grading scales for knee OA:global,composite and individual feature scales.Each grade on a global scale describes one or more features of knee OA.The entire description must be met for a specific grade to be assigned.The KellgrenLawrence scale is the most commonly-used global scale.Composite scales grade several features of knee OA individually and sum the grades to create a total score.One example is the compartmental grading scale for knee OA.Composite scales can respond to change in a variety of presentations of knee OA.Individual feature scales assess one or more OA features individually and do not calculate a total score.They are most often used to monitor change in one OA feature,commonly joint space narrowing.The most commonly-used individual feature scale is the OA Research Society International atlas.Each type of scale has its advantages;however,composite scales may offer greater content validity.Responsiveness to change is unknown for most scales and deserves further evaluation.展开更多
文摘详细论述了有限元的基本理论,根据实际情况,考虑船舶推进轴系校中计算中剪切变形的影响,对有限元法的刚度矩阵进行了改进。利用V B.N ET 开发了船舶推进轴系校中计算通用软件,通过与没有考虑剪切变形的国内外同类计算软件计算结果的比较以及实际中的应用,表明了这种改进是合理的且可以获得更准确的结果。所开发的计算软件,界面友好,功能完善,操作简单,满足轴系设计计算、校核计算的需要,进一步完善了船舶推进轴系校中计算模型,便于二次开发与深入研究。
基金Project (No. 60337030) partly supported by the National NaturalScience Foundation of China
文摘Shaft alignment is an important technique during installation and maintenance of a rotating machine. A high-precision laser alignment system has been designed with dual PSDs (Position Sensing Detector) to change traditional manual way of shaft alignment and to make the measurement easier and more accurate. The system is comprised of two small measuring units (laser transmitter and detector) and a PDA (Personal Digital Assistant) with measurement software. The laser alignment system with dual PSDs was improved on a single PSD system, and yields higher measurement accuracy than the previous design, and has been successful for designing and implements actual shaft alignment. In the system, the range of offset measurement is ±4 mm, and the resolution is 1.5 μm, with accuracy being less than 2 μm.
文摘Knee osteoarthritis(OA) is a progressive joint disease hallmarked by cartilage and bone breakdown and associated with changes to all of the tissues in the joint,ultimately causing pain,stiffness,deformity and disability in many people.Radiographs are commonly used for the clinical assessment of knee OA incidence and progression,and to assess for risk factors.One risk factor for the incidence and progression of knee OA is malalignment of the lower extremities(LE).The hipknee-ankle(HKA) angle,assessed from a full-length LE radiograph,is ideally used to assess LE alignment.Careful attention to LE positioning is necessary to obtain the most accurate measurement of the HKA angle.Since full-length LE radiographs are not always available,the femoral shaft-tibial shaft(FS-TS) angle may be calculated from a knee radiograph instead.However,the FS-TS angle is more variable than the HKA angle and it should be used with caution.Knee radiographs are used to assess the severity of knee OA and its progression.There are three types of ordinal grading scales for knee OA:global,composite and individual feature scales.Each grade on a global scale describes one or more features of knee OA.The entire description must be met for a specific grade to be assigned.The KellgrenLawrence scale is the most commonly-used global scale.Composite scales grade several features of knee OA individually and sum the grades to create a total score.One example is the compartmental grading scale for knee OA.Composite scales can respond to change in a variety of presentations of knee OA.Individual feature scales assess one or more OA features individually and do not calculate a total score.They are most often used to monitor change in one OA feature,commonly joint space narrowing.The most commonly-used individual feature scale is the OA Research Society International atlas.Each type of scale has its advantages;however,composite scales may offer greater content validity.Responsiveness to change is unknown for most scales and deserves further evaluation.
