A mathematical energy coupling model was developed to analyze the light transmission in the keyhole and energy distribution on the keyhole wall.The main characteristics of the model include：1） a prototype of the key...A mathematical energy coupling model was developed to analyze the light transmission in the keyhole and energy distribution on the keyhole wall.The main characteristics of the model include：1） a prototype of the keyhole and the inverse Bremsstrahlung absorption coefficient in the keyhole plasma are obtained from the experiments;2） instead of using a parallel incident beam,a focused laser beam with real Gaussian intensity distribution is implemented;3） both Fresnel absorption and inverse Bremsstrahlung absorption during multiple reflections are considered.The calculation results show that the distribution of absorbed laser intensity by the keyhole wall is not uniform.The maximum laser energy is absorbed by the bottom of the keyhole,although no rays irradiate directly onto the bottom.According to analysis of beam focusing characteristics,the location of the focal plane plays a more important role in the laser energy absorption by the front wall than by the rear wall.展开更多
This paper is a review of the past research of mechanical testing methods for natural fibre honeycomb sandwich structure as well as failure modes analysis at a microscopic level by using Scanning Electron Microscope (...This paper is a review of the past research of mechanical testing methods for natural fibre honeycomb sandwich structure as well as failure modes analysis at a microscopic level by using Scanning Electron Microscope (SEM). As the world is garnering attention towards renewable resources for environmental purposes, studies of natural fibre have been increasing as well as the application of natural fibre throughout various industries such as aerospace, automobiles, and construction sectors. This paper is started with brief information regarding the honeycomb sandwich structure, introduction to natural fibre, its applications as well as the factors affecting the performances of the structure. Next, the mechanical testing methods are listed out as well as the expected outcomes obtained from the respective testing. The mechanical properties are also identified by conducting lab tests according to the ASTM standard for sandwich and core structures. The microstructure of the deformed samples is then examined under Scanning Electron Microscope (SEM) by using different magnifications to study the failure mechanisms of the samples. The images obtained from the SEM test are analyzed by using fractography which will show the failure modes of the samples. This article is based on past research conducted by professional on the related topic.展开更多
目的探究启发式临床医学教学模式(problem-originated clinical medical curriculum,PCMC)联合三明治(Sandwich)教学法在神经内科本科学教学中的应用效果。方法选取2018年6月—2019年6月在东莞市厚街医院神经内科接受本科教学的医学生86...目的探究启发式临床医学教学模式(problem-originated clinical medical curriculum,PCMC)联合三明治(Sandwich)教学法在神经内科本科学教学中的应用效果。方法选取2018年6月—2019年6月在东莞市厚街医院神经内科接受本科教学的医学生86名,均接受了为期6个月的教学,采取随机数字表法分为对照组与观察组,各43名,对照组给予常规教学方法,观察组实施PCMC联合Sandwich教学法,教学内容同对照组,对比两组医学生的理论考试与实践技能成绩,医学生学习能力,医学生对教学方法的评价,医学生对教学效果、授课方式以及学时安排的满意度。结果观察组与对照组相比,理论考试中基础知识以及病例分析的成绩较高,实践技能考试中技能操作能力、健康宣教能力、沟通能力以及人文素养的成绩较高,差异有统计学意义(P<0.05)。观察组与对照组相比提高医学生自我管理能力、促进自主学习能力、促进学习积极性、促进生生互动以及促进师生互动的评分均较高,差异有统计学意义(P<0.05)。观察组与对照组相比,认为技能操作配合好、认为反馈和指导正确、认为能够提高学习积极性与主动性、认为可巩固理论知识、认为可增强实践动手能力、认为可提高与患者的沟通能力、认为可提高面对患者时的能力与信心的比例较高,差异有统计学意义(P<0.05)。观察组与对照组相比,医学生对教学效果、授课方式以及学时安排的满意度均较高,差异有统计学意义(P<0.05)。结论PCMC联合Sandwich教学法在神经内科本科学教学中的应用明显提高了教学质量及医学生成绩,医学生对教学结果评价更好,满意度更高。展开更多
Sandwich panel is commonly used in ship and marine engineering equipment,such as side structure and superstructure deck of a ship,which is of good anti-explosion performance.This paper addresses a study on the dynamic...Sandwich panel is commonly used in ship and marine engineering equipment,such as side structure and superstructure deck of a ship,which is of good anti-explosion performance.This paper addresses a study on the dynamic response of the U-typed sandwich panel under explosion load through the numerical simulation and theoretical methods.Based on the orthotropic plate theory,the U-typed sandwich panel is simplified and transformed into a single degree of freedom(SDOF)spring system,the equivalent motion equation of the SDOF system and the expression of triangular explosion load function are established based on the SDOF theory,and the maximum response spectrum of the SDOF system is obtained.Then,the response of the equivalent SDOF system of the U-typed sandwich panel under explosion load is analyzed,and the theoretical results match well with the numerical simulation results,which verifies the accuracy of the theoretical method proposed in this paper.The theoretical method proposed in this paper could have good engineering applications for the structural anti-explosion design,and provide a reference for the evaluation of the anti-explosion performance of ship and offshore platform structures.展开更多
The present study explored the influence of axial gradation of viscoelastic materials on the dynamic response of the sandwich beam for structural applications.The finite element(FE)formulations are used to model and i...The present study explored the influence of axial gradation of viscoelastic materials on the dynamic response of the sandwich beam for structural applications.The finite element(FE)formulations are used to model and investigate dynamic response of the sandwich beam.The classical beam theory is used to develop the FE formulations and Lagrange's approach is considered to obtain the equations of motion(EOM).FE code is developed and validated with the existing literature and also conducted the convergence study for the developed FE method.Further,the influence of different viscoelastic materials and boundary conditions on the dynamic response of the sandwich beam is investigated.Four different axial gradation configurations of viscoelastic materials are considered for the present work to explore the influence on natural frequency,loss factor and frequency response of the sandwich beam.The modeled axial gradation of viscoelastic material has displayed a considerable impact on the peak vibrational amplitude response of the sandwich beam for all the boundary conditions and these configurations improved the damping capabilities at different configurations for the structural applications.展开更多
基金Projects (51175162, 50805045) supported by the National Natural Science Foundation of ChinaProject supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education,China
文摘A mathematical energy coupling model was developed to analyze the light transmission in the keyhole and energy distribution on the keyhole wall.The main characteristics of the model include：1） a prototype of the keyhole and the inverse Bremsstrahlung absorption coefficient in the keyhole plasma are obtained from the experiments;2） instead of using a parallel incident beam,a focused laser beam with real Gaussian intensity distribution is implemented;3） both Fresnel absorption and inverse Bremsstrahlung absorption during multiple reflections are considered.The calculation results show that the distribution of absorbed laser intensity by the keyhole wall is not uniform.The maximum laser energy is absorbed by the bottom of the keyhole,although no rays irradiate directly onto the bottom.According to analysis of beam focusing characteristics,the location of the focal plane plays a more important role in the laser energy absorption by the front wall than by the rear wall.
文摘This paper is a review of the past research of mechanical testing methods for natural fibre honeycomb sandwich structure as well as failure modes analysis at a microscopic level by using Scanning Electron Microscope (SEM). As the world is garnering attention towards renewable resources for environmental purposes, studies of natural fibre have been increasing as well as the application of natural fibre throughout various industries such as aerospace, automobiles, and construction sectors. This paper is started with brief information regarding the honeycomb sandwich structure, introduction to natural fibre, its applications as well as the factors affecting the performances of the structure. Next, the mechanical testing methods are listed out as well as the expected outcomes obtained from the respective testing. The mechanical properties are also identified by conducting lab tests according to the ASTM standard for sandwich and core structures. The microstructure of the deformed samples is then examined under Scanning Electron Microscope (SEM) by using different magnifications to study the failure mechanisms of the samples. The images obtained from the SEM test are analyzed by using fractography which will show the failure modes of the samples. This article is based on past research conducted by professional on the related topic.
文摘目的探究启发式临床医学教学模式(problem-originated clinical medical curriculum,PCMC)联合三明治(Sandwich)教学法在神经内科本科学教学中的应用效果。方法选取2018年6月—2019年6月在东莞市厚街医院神经内科接受本科教学的医学生86名,均接受了为期6个月的教学,采取随机数字表法分为对照组与观察组,各43名,对照组给予常规教学方法,观察组实施PCMC联合Sandwich教学法,教学内容同对照组,对比两组医学生的理论考试与实践技能成绩,医学生学习能力,医学生对教学方法的评价,医学生对教学效果、授课方式以及学时安排的满意度。结果观察组与对照组相比,理论考试中基础知识以及病例分析的成绩较高,实践技能考试中技能操作能力、健康宣教能力、沟通能力以及人文素养的成绩较高,差异有统计学意义(P<0.05)。观察组与对照组相比提高医学生自我管理能力、促进自主学习能力、促进学习积极性、促进生生互动以及促进师生互动的评分均较高,差异有统计学意义(P<0.05)。观察组与对照组相比,认为技能操作配合好、认为反馈和指导正确、认为能够提高学习积极性与主动性、认为可巩固理论知识、认为可增强实践动手能力、认为可提高与患者的沟通能力、认为可提高面对患者时的能力与信心的比例较高,差异有统计学意义(P<0.05)。观察组与对照组相比,医学生对教学效果、授课方式以及学时安排的满意度均较高,差异有统计学意义(P<0.05)。结论PCMC联合Sandwich教学法在神经内科本科学教学中的应用明显提高了教学质量及医学生成绩,医学生对教学结果评价更好,满意度更高。
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51779110 and 51809122)the Natural Science Foundation of Jiangsu Province(Grant No.BK20191461)the Six Talent Peaks Project in Jiangsu Province(Grant No.KTHY-064).
文摘Sandwich panel is commonly used in ship and marine engineering equipment,such as side structure and superstructure deck of a ship,which is of good anti-explosion performance.This paper addresses a study on the dynamic response of the U-typed sandwich panel under explosion load through the numerical simulation and theoretical methods.Based on the orthotropic plate theory,the U-typed sandwich panel is simplified and transformed into a single degree of freedom(SDOF)spring system,the equivalent motion equation of the SDOF system and the expression of triangular explosion load function are established based on the SDOF theory,and the maximum response spectrum of the SDOF system is obtained.Then,the response of the equivalent SDOF system of the U-typed sandwich panel under explosion load is analyzed,and the theoretical results match well with the numerical simulation results,which verifies the accuracy of the theoretical method proposed in this paper.The theoretical method proposed in this paper could have good engineering applications for the structural anti-explosion design,and provide a reference for the evaluation of the anti-explosion performance of ship and offshore platform structures.
基金support from the Department of Science and Technology (DST)file no.ECR/2016/001448 titled“Experimental Investigation of Passive,Semi-active and Active vibration control of Composite Sandwich Structure”funded by Science and Engineering Research Board,Government of India。
文摘The present study explored the influence of axial gradation of viscoelastic materials on the dynamic response of the sandwich beam for structural applications.The finite element(FE)formulations are used to model and investigate dynamic response of the sandwich beam.The classical beam theory is used to develop the FE formulations and Lagrange's approach is considered to obtain the equations of motion(EOM).FE code is developed and validated with the existing literature and also conducted the convergence study for the developed FE method.Further,the influence of different viscoelastic materials and boundary conditions on the dynamic response of the sandwich beam is investigated.Four different axial gradation configurations of viscoelastic materials are considered for the present work to explore the influence on natural frequency,loss factor and frequency response of the sandwich beam.The modeled axial gradation of viscoelastic material has displayed a considerable impact on the peak vibrational amplitude response of the sandwich beam for all the boundary conditions and these configurations improved the damping capabilities at different configurations for the structural applications.
