Analysis of Linear and Nonlinear Vibrations of Composite Rectangular Sandwich Plates with Lattice Cores

For the first time,the linear and nonlinear vibrations of composite rectangular sandwich plates with various geometric patterns of lattice core have been analytically examined in this work.The plate comprises a lattice core located in the middle and several homogeneous orthotropic layers that are symmetrical relative to it.For this purpose,the partial differential equations of motion have been derived based on the first-order shear deformation theory,employing Hamilton’s principle and Von Kármán’s nonlinear displacement-strain relations.Then,the nonlinear partial differential equations of the plate are converted into a time-dependent nonlinear ordinary differential equation(Duffing equation)by applying the Galerkin method.From the solution of this equation,the natural frequencies are extracted.Then,to calculate the non-linear frequencies of the plate,the non-linear equation of the plate has been solved analytically using the method of multiple scales.Finally,the effect of some critical parameters of the system,such as the thickness,height,and different angles of the stiffeners on the linear and nonlinear frequencies,has been analyzed in detail.To confirmthe solution method,the results of this research have been compared with the reported results in the literature and finite elements in ABAQUS,and a perfect match is observed.The results reveal that the geometry and configuration of core ribs strongly affect the natural frequencies of the plate.

PBL-Sandwich混合教学模式在临床分子生物学检验技术实习教学中的应用

目的 探讨以问题为基础的教学法(PBL)-Sandwich混合教学模式在临床分子生物学检验技术实习教学中的应用效果。方法 选取2018-2019年进入该院分子生物学实验室实习的82例实习生作为研究对象。以2018年的42例实习生作为对照组,采用传统教学模式;以2019年的40例实习生作为试验组,采用PBL-Sandwich混合教学模式。实习结束后,采用理论考试、操作考核和问卷调查等形式评价实习生的教学效果。结果 试验组的理论考试成绩与操作考核成绩均明显高于对照组,差异均有统计学意义(P<0.05)。共发放调查问卷82份,回收有效问卷80份,其中试验组39份,对照组41份,有效回收率为97.56%(80/82)。试验组在提高学习主动性、激发学习兴趣、增强师生间的交流和互动、提升分析解决临床实际问题能力和教学方法实施满意度方面均优于对照组,差异均有统计学意义(P<0.05)。结论 PBL-Sandwich混合教学模式能有效激发实习生学习兴趣,培养实习生自主学习的主观能动性,提高分析、解决临床实际问题能力,教学质量得到提升。

MDT+Sandwich教学法在本科内科学教学中的应用

目的探讨多学科诊疗(MDT)+“三明治”教学法(Sandwich教学法)与传统的以学科为基础的教学法在本科内科学教学中的应用效果。方法选取五年制临床医学专业60名本科生为研究对象,随机分为对照组(n=30)和试验组(n=30)。对照组采用传统的以学科为基础的教学法,试验组采用MDT+Sandwich教学法,课程结束后比较两组教学效果。结果试验组理论考试、临床技能操作考核成绩及课堂教学效果均优于对照组。结论在内科学教学中引入MDT+Sandwich教学法,能够更好地培养学生分析和解决临床问题能力。

基于微课嵌入的Sandwich教学法在诊断病理学教学中的应用

目的:探讨基于微课嵌入的Sandwich教学法在诊断病理学教学中的应用效果。方法:选取3个班级,随机分为试验组、对照组和空白对照组,分别采用不同的教学方法进行教学。结果:试验组学生的成绩显著优于对照组和空白对照组;试验组学生对该教学方法的认可度较高,教师对试验组学生的课堂表现评价也较高。结论:基于微课嵌入的Sandwich教学模式在诊断病理学教学中具有良好的应用效果,值得进一步推广。

Sandwich联合角色扮演教学法在住培医师医患沟通能力培训中的应用

目的 以腰椎穿刺术前谈话为例,探讨Sandwich联合角色扮演教学法在住院医师规范化培训(住培)学员医患沟通能力培训中的应用价值。方法 选取2019年3月至2023年1月在该院神经外科进行住培的40名学员,将其分为A、B组,每组20名。A组通过传统教学方法进行腰椎穿刺术前谈话的教学,B组运用Sandwich联合角色扮演教学法进行教学,在教学前、中、后期分别使用医患沟通技能评价量表对2组学员进行考评,最后对2组学员进行满意度问卷调查,对比2组教学效果及学员对教学的满意度。结果 2组学员在教学前测评得分均较低,在教学后测评较教学前均有提升,差异均有统计学意义(P<0.05);与A组比较,B组在教学中期测评得分明显更高,差异有统计学意义(P<0.05);2组在教学后期测评得分比较,差异无统计学意义(P>0.05)。B组住培学员的满意度高于A组,差异有统计学意义(P<0.05)。结论 Sandwich联合角色扮演教学法能快速提升学员的术前谈话沟通能力,也能提高学员的教学满意度,适合在相关教学活动中推广。

基于CBL+PBL联合Sandwich教学法在神经病学本科教学中的探索

神经病学是一门理论性和实践性较强的综合性学科,对从业人员的专业知识和操作技能均有较高要求。传统神经病学本科教育存在教师单方面授课无法激发学生学习兴趣、学生学习有效性不足等问题,使神经病学专业人才的培养存在一定难度。该文基于神经病学本科教学的实际情况,探讨以CBL、PBL联合Sandwich教学法在神经病学专业本科教育体系中的应用前景。

案例教学法联合Sandwich教学法在老年科教学中的应用

目的探讨案例教学法联合Sandwich教学法在老年科教学中的应用效果。方法选取2022年3月—2023年6月潍坊医学院附属医院的60名参加老年科教学的学生为研究对象,按照随机数表法分为两组,各30名。对照组行常规教学,观察组行案例教学法联合Sandwich教学法教学,比较两组教学效果。结果观察组各项模拟出科考试成绩高于对照组,差异有统计学意义(P均<0.05);观察组对实习教学效果的各项满意度评分高于对照组,差异有统计学意义(P<0.05)。结论案例教学法联合Sandwich教学法可提升老年科教学的效果,并提高学生对实习教学效果的满意度。

Sandwich教学法融入思政教育在超声诊断学中的应用

研究Sandwich教学法融入思政教育模式在超声诊断学教学中应用效果。方法 选择2022年11月-2023年11月在本院接受超声诊断学教学的学生40名,随机分组法分作试验组(Sandwich教学法融入思政教育模式)和对照组(传统教学模式),每组20名,分析不同教学模式的实施效果评价。结果 出科时,试验组考核成绩明显高于对照组,P<0.05;试验组综合能力和批判性思维能力均优于对照组,P<0.05。结论 超声诊断学教学中实施Sandwich教学法融入思政教育模式,可明显提升学生考核成绩、综合素质以及批判性思维能力,可以应用于超声诊断学教学。

Sandwich教学方法在非本专业医学本科生临床见习中的应用效果

目的:探讨Sandwich教学方法应用于非麻醉专业本科生在麻醉临床见习中的应用效果。方法:本研究选择2021年4月在首都医科大学附属北京佑安医院参与临床麻醉学见习的51名本科护理学专业学生作为观察对象,根据随机表随机分为对照组(n=26)和试验组(n=25)。其中对照组采用常规的见习教学方法,而试验组采用Sandwich教学方法,最后两组采用理论知识试卷和满意度调查表进行教学效果和教师满意度评价。结果:理论知识掌握方面,试验组和对照组的平均得分分别是(81.80±5.02)分与(66.56±5.13)分,差异具有统计学意义(P<0.05);对见习带教老师满意度方面,试验组显著高于对照组,差异具有统计学意义(P<0.05)。结论:Sandwich教学方法不仅有利于见习生掌握教学大纲内容,而且还有利于提高学生对带教老师的满意度。

含根量对SANDWICH形加筋土界面剪切强度影响--以红叶石楠为例

SANDWICH形加筋土是一种采用粘土夹砂层以及土工格栅而形成的混合填料形式的加筋土结构。采用一系列直接剪切试验研究含根量、竖向应力等因素对筋土界面强度的影响。试验证明,根系的加入对SANDWICH形加筋土界面最大剪应力有所提升且随着竖向应力的增大,土体抗剪强度增幅大。随着粘土中含根量的增加,筋土界面最大剪应力在不同竖向应力作用下出现先增后减的趋势。根据试验数据,利用拟合软件提出了评价筋土界面剪切强度的经验公式,得出理论上含根量的最优值为4.2%。并通过试验验证了拟合公式的有效性和正确性。

Mechanical Performance of Bio-inspired Bidirectional Corrugated Sandwich Pressure Shell Under External Hydrostatic Pressure

This paper aims to enhance the compression capacity of underwater cylindrical shells by adopting the corrugated sandwich structure of cuttlebone.The cuttlebone suffers uniaxial external compression,while underwater cylindrical shells are in a biaxial compressive stress state.To suit the biaxial compressive stress state,a novel bidirectional corrugated sandwich structure is proposed to improve the bearing capacity of cylindrical shells.The static and buckling analysis for the sandwich shell and the unstiffened cylindrical shell with the same volume-weight ratio are studied by numerical simulation.It is indicated that the proposed sandwich shell can effectively reduce the ratio between circumferential and axial stress from 2 to 1.25 and improve the critical buckling load by about 1.63 times.Numerical simulation shows that optimizing and adjusting the structural parameters could significantly improve the advantage of the sandwich shell.Then,the hydrostatic pressure tests for shell models fabricated by 3D printing are carried out.According to the experimental results,the overall failure position of the sandwich shell is at the center part of the sandwich shell.It has been found the average critical load of the proposed sandwich shell models exceeds two times that of the unstiffened shell models.Hence,the proposed bio-inspired bidirectional corrugated sandwich structure can significantly enhance the pressure resistance capability of cylindrical shells.

Dynamic and electrical responses of a curved sandwich beam with glass reinforced laminate layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact

The dynamic responses and generated voltage in a curved sandwich beam with glass reinforced laminate(GRL)layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact(LVI)are investigated.The current study aims to carry out a dynamic analysis on the sandwich beam when the impactor hits the top face sheet with an initial velocity.For the layer analysis,the high-order shear deformation theory(HSDT)and Frostig's second model for the displacement fields of the core layer are used.The classical non-adhesive elastic contact theory and Hunter's principle are used to calculate the dynamic responses in terms of time.In order to validate the analytical method,the outcomes of the current investigation are compared with those gained by the experimental tests carried out by other researchers for a rectangular composite plate subject to the LVI.Finite element(FE)simulations are conducted by means of the ABAQUS software.The effects of the parameters such as foam modulus,layer material,fiber angle,impactor mass,and its velocity on the generated voltage are reviewed.

基于岗位胜任力的WebQuest联合Sandwich教学法在超声医学本科教学的探索

超声医学是一门理论性和实践性较强的综合性学科,对从业人员的专业知识和操作技能均有较高要求。传统超声医学本科教育存在教师单方面授课无法激发学生学习兴趣以及学生实践时间严重不足等问题,超声医学专业人才岗位胜任力的培养存在一定难度。本文基于超声医学本科教学的实际情况,探讨以岗位胜任力为导向的WebQuest联合Sandwich教学法在超声医学专业本科教育体系中的应用前景。

sandwich教学法结合消化内镜教学在消化内科临床教学中的应用研究

目的:探讨“三明治”(sandwich)教学法结合消化内镜教学在消化内科临床实习教学中的应用效果。方法:选取2019年4月至2019年11月来我院消化内科实习的169名本科学生作为研究对象,将单月的实习医生85名作为试验组,双月的实习医生84名作为对照组。试验组采用sandwich教学法结合消化内镜教学,对照组采用传统教学方式。通过出科考试和问卷调查对教学效果进行评估。结果:试验组与对照组相比,基础知识成绩无明显差异(P>0.05),但试验组病例分析成绩明显优于对照组,差异具有统计学意义(P<0.05)。满意度调查显示试验组中各项满意度均明显高于对照组,差异有统计学意义(P<0.05)。结论:sandwich教学法结合消化内镜教学模式在推动理论和临床实践的渗透中具有积极促进作用,能明显改善、提高教学效果和教学满意度,在消化内科临床实习教学中值得推广。

MDT模式下Sandwich教学法在护理临床教学活动中的应用

目的探讨多学科协作诊疗(MDT)模式下Sandwich教学法在护理临床教学活动中的应用效果。方法选取2021-2023学年在重庆市铜梁区人民医院实习的两批护理学生共197人为研究对象,采取非同期对照研究方法,将2021-2022学年实习护生纳入对照组(n=86),2022-2023学年实习护生纳入观察组(n=111)。在临床护理教学活动中,观察组护生采用MDT模式下Sandwich教学法,对照组护生采用传统教学法。实习结束前进行理论操作考核,同时对2组护生的临床思维能力、学习主动性进行问卷调查。结果观察组护生的理论操作考试成绩,临床思维能力量表、学习主动性量表评分均高于对照组,差异均有统计学意义(P<0.05)。结论MDT模式下Sandwich教学法能够促进学生对护理专业知识的掌握,提高其临床思维能力、自主学习能力,课堂教学效果较好,值得推广。

非k积态基于Sandwiched Renyi相对熵的关联测度

在量子信息理论中,Sandwiched Renyi相对熵具有极其重要的应用价值。该研究给出多体复合系统非k积态基于Sandwiched Renyi相对熵的关联测度,同时证明了其满足量子关联度的一些必要性质,包括非负性,酉不变性,在完全正的保迹线性映射下的单调性,联合凸性以及在非相干辅助子系统影响下的不变性。

Sandwich联合CBL在急诊护理实习生带教中的应用

探讨Sandwich教学法联合案例教学法(CBL)在急诊护理实习生带教中的应用效果。方法 本研究于2024年1月至9月期间,对60名急诊护理实习生实施Sandwich联合CBL教学法进行带教。实习生被随机分为联合组和对照组,各30人。联合组采用Sandwich联合CBL教学法,对照组则采用传统教学法。比较两组理论考核成绩、操作考试成绩、自主学习能力及实习生对教学的满意度。结果 联合组的理论考核成绩分数、操作考试成绩分数、自主学习能力评分及教学满意度评分均大于对照组(P<0.05)。结论 Sandwich教学法联合CBL能够有效提高急诊护理实习生的综合素质和满意度,值得在护理教学中推广应用。

Sandwich structures with tapered tubes as core:A quasi-static investigation

In this article,the experimental and finite element analysis is utilized to investigate the quasi-static compression features of sandwich constructions built with tapered tubes.3D printing technology was utilized to create the hollow centers of the tapering tubes,with and without corrugations.The results demonstrate that the energy absorption(EA)and specific energy absorption(SEA)of the single corrugated tapered tube sandwich are 51.6% and 19.8% higher,respectively,than those of the conical tube sandwich.Furthermore,the results demonstrate that energy absorbers can benefit from corrugation in order to increase their efficiency.Additionally,the tapered corrugated tubes'resistance to oblique impacts was studied.Compared to a straight tube,the tapered tube is more resistant to oblique loads and has a lower initial peak crushing force(PCF),according to numerical simulations.After conducting a parametric study,it was discovered that the energy absorption performance of the sandwich construction is significantly affected by the amplitude,number of corrugations,and wall thickness.EA and SEA of DTS with corrugation number of 8 increased by 17.4%and 29.6%,respectively,while PCF decreased by 9.2% compared to DTS with corrugation number of 10.

Dynamic Resistance and Energy Absorption of Sandwich Beam via a Micro-Topology Optimization

The current research of sandwich structures under dynamic loading mainly focus on the response characteristic of structure.The micro-topology of core layers would sufficiently influence the property of sandwich structure.However,the micro deformation and topology mechanism of structural deformation and energy absorption are unclear.In this paper,based on the bi-directional evolutionary structural optimization method and periodic base cell(PBC)technology,a topology optimization frame work is proposed to optimize the core layer of sandwich beams.The objective of the present optimization problem is to maximize shear stiffness of PBC with a volume constraint.The effects of the volume fraction,filter radius,and initial PBC aspect ratio on the micro-topology of the core were discussed.The dynamic response process,core compression,and energy absorption capacity of the sandwich beams under blast impact loading were analyzed by the finite element method.The results demonstrated that the overpressure action stage was coupled with the core compression stage.Under the same loading and mass per unit area,the sandwich beam with a 20%volume fraction core layer had the best blast resistance.The filter radius has a slight effect on the shear stiffness and blast resistances of the sandwich beams.But increasing the filter radius could slightly improve the bending stiffness.Upon changing the initial PBC aspect ratio,there are three ways for PBC evolution:The first is to change the angle between the adjacent bars,the second is to further form holes in the bars,and the third is to combine the first two ways.However,not all three ways can improve the energy absorption capacity of the structure.Changing the aspect ratio of the PBC arbitrarily may lead to worse results.More studies are necessary for further detailed optimization.This research proposes a new topology sandwich beam structure by micro-topology optimization,which has sufficient shear stiffness.The micro mechanism of structural energy absorption is clarified,it is significant for structural energy absorption design.

Nonlinear vibration of Timoshenko FG porous sandwich beams subjected to a harmonic axial load

In this study,the instability and bifurcation diagrams of a functionally graded(FG)porous sandwich beam on an elastic,viscous foundation which is influenced by an axial load,are investigated with an analytical attitude.To do so,the Timoshenko beam theory is utilized to take the shear deformations into account,and the nonlinear Von-Karman approach is adopted to acquire the equations of motion.Then,to turn the partial differential equations(PDEs)into ordinary differential equations(ODEs)in the case of equations of motion,the method of Galerkin is employed,followed by the multiple time scale method to solve the resulting equations.The impact of parameters affecting the response of the beam,including the porosity distribution,porosity coefficient,temperature increments,slenderness,thickness,and damping ratios,are explicitly discussed.It is found that the parameters mentioned above affect the bifurcation points and instability of the sandwich porous beams,some of which,including the effect of temperature and porosity distribution,are less noticeable.