Prediction of Compressive and Shear Moduli of X-cor Sandwich Structures for Aeronautic Engineering

The so-called″X-cor sandwich structure″is a highly promising novel material as an alternative to honeycomb used in aircraft.Although much work has been conducted on the performance of the X-cor sandwich structure,the gap is still hardly bridged between experimental results and theoretical analyses.Therefore,a method has been innovated to establish semi-empirical formula for the prediction of compressive and shear moduli of X-cor sandwich structure composites,by combining theoretical analyses and experimental data.In addition,aprediction software was first developed based on the proposed method,of which the accuracy was verified through confirmatory experiments.This software can offer a direct reference or guide for engineers in structural designing.

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。

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。

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。

Phonon Thermal Transport at Interfaces of a Graphene/Vertically Aligned Carbon Nanotubes/Hexagonal Boron Nitride Sandwiched Heterostructure

Molecular dynamics simulation is used to calculate the interfacial thermal resistance of a graphene/carbon nanotubes/hexagonal boron nitride(Gr/CNTs/hBN)sandwiched heterostructure,in which vertically aligned carbon nanotube(VACNT)arrays are covalently bonded to graphene and hexagonal boron nitride layers.We find that the interfacial thermal resistance(ITR)of the Gr/VACNT/hBN sandwiched heterostructure is one to two orders of magnitude smaller than the ITR of a Gr/hBN van der Waals heterostructure with the same plane size.It is observed that covalent bonding effectively enhances the phonon coupling between Gr and hBN layers,resulting in an increase in the overlap factor of phonon density of states between Gr and hBN,thus reducing the ITR of Gr and hBN.In addition,the chirality,size(diameter and length),and packing density of sandwich-layer VACNTs have an important influence on the ITR of the heterostructure.Under the same CNT diameter and length,the ITR of the sandwiched heterostructure with armchair-shaped VACNTs is higher than that of the sandwiched heterostructure with zigzag-shaped VACNTs due to the different chemical bonding of chiral CNTs with Gr and hBN.When the armchair-shaped CNT diameter increases or the length decreases,the ITR of the sandwiched heterostructure tends to decrease.Moreover,the increase in the VACNT packing density also leads to a continuous decrease in the ITR of the sandwiched heterostructure,attributed to the extremely high intrinsic thermal conductivity of CNTs and the increase of out-of-plane heat transfer channels.This work may be helpful for understanding the mechanism for ITR in multilayer vertical heterostructures,and provides theoretical guidance for a new strategy to regulate the interlayer thermal resistance of heterostructures by optimizing the design of sandwich layer thermal interface materials.

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.

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.

Energy dissipation mechanism and ballistic characteristic optimization in foam sandwich panels against spherical projectile impact

This study systematically examines the energy dissipation mechanisms and ballistic characteristics of foam sandwich panels(FSP)under high-velocity impact using the explicit non-linear finite element method.Based on the geometric topology of the FSP system,three FSP configurations with the same areal density are derived,namely multi-layer,gradient core and asymmetric face sheet,and three key structural parameters are identified:core thickness(t_(c)),face sheet thickness(t_(f))and overlap face/core number(n_(o)).The ballistic performance of the FSP system is comprehensively evaluated in terms of the ballistic limit velocity(BLV),deformation modes,energy dissipation mechanism,and specific penetration energy(SPE).The results show that the FSP system exhibits a significant configuration dependence,whose ballistic performance ranking is:asymmetric face sheet>gradient core>multi-layer.The mass distribution of the top and bottom face sheets plays a critical role in the ballistic resistance of the FSP system.Both BLV and SPE increase with tf,while the raising tcor noleads to an increase in BLV but a decrease in SPE.Further,a face-core synchronous enhancement mechanism is discovered by the energy dissipation analysis,based on which the ballistic optimization procedure is also conducted and a design chart is established.This study shed light on the anti-penetration mechanism of the FSP system and might provide a theoretical basis for its engineering application.

Mechanical property of cylindrical sandwich shell with gradient core of entangled wire mesh

To explore the wide-frequency damping and vibration-attenuation performances in the application of aerospace components,the cylindrical sandwich shell structure with a gradient core of entangled wire mesh was proposed in this paper.Firstly,the gradient cores of entangled wire mesh in the axial and radial directions were prepared by using an in-house Numerical Control weaving machine,and the metallurgical connection between skin sheets and the gradient core was performed using vacuum brazing.Secondly,to investigate the mechanical properties of cylindrical sandwich shells with axial or radial gradient cores,quasi-static and dynamic mechanical experiments were carried out.The primary evaluations of mechanical properties include secant stiffness,natural frequency,Specific Energy Absorption(SEA),vibration acceleration level,and so on.The results suggest that the vibration-attenuation performance of the sandwich shell is remarkable when the high-density core layer is at the end of the shell or abuts the inner skin.The axial gradient material has almost no influence on the vibration frequencies of the shell,whereas the vibration frequencies increase dramatically when the high-density core layer approaches the skin.Moreover,compared to the conventional sandwich shells,the proposed functional grading cylindrical sandwich shell exhibits more potential in mass reduction,stiffness designing,and energy dissipation.

Double casing warhead with sandwiched charge:The axial distribution of fragments velocities

The double casing warhead with sandwiched charge is a novel fragmentation warhead that can produce two groups of fragments with different velocity,and the previous work has presented a calculation formula to determine the maximum fragment velocity.The current work builds on the published formula to further develop a formula for calculating the axial distribution characteristics of the fragment velocity.For this type of warhead,the simulation of the dispersion characteristics of the detonation products at different positions shows that the detonation products at the ends have a much larger axial velocity than those in the middle,and the detonation products have a greater axial dispersion velocity when they are closer to the central axis.The loading process and the fragment velocity vary with the axial position for both casing layers,and the total velocity of the fragments is the vector sum of the radial velocity and the axial velocity.At the same axial position,the acceleration time of the inner casing is greater than that of the outer casing.For the same casing,the fragments generated at the ends have a longer acceleration time than the fragments from the middle.The proposed formula is validated with the X-ray radiography results of the four warheads previously tested experimentally and the 3D smoothedparticle hydrodynamics numerical simulation results of several series of new warheads with different configurations.The formula can accurately and reliably calculate the fragment velocity when the lengthto-diameter ratio of the charge is greater than 1.5 and the thickness of the casing is less than 20%its inner radius.This work thus provides a key reference for the theoretical analysis and the design of warheads with multiple casings.

Ballistic performances of the hourglass lattice sandwich structures under high-velocity fragments

In this paper,the numerical simulation method is used to study the ballistic performances of hourglass lattice sandwich structures with the same mass under the vertical incidence of fragments.Attention is paid to elucidating the influences of rod cross-section dimensions,structure height,structure layer,and rod inclination angle on the deformation mode,ballistic performances,and ability to change the ballistic direction of fragments.The results show that the ballistic performances of hourglass lattice sandwich structures are mainly affected by their structural parameters.In this respect,structural parameters optimization of the hourglass lattice sandwich structures enable one to effectively improve their ballistic limit velocity and,consequently,ballistic performances.

Sandwich教学法在中医骨伤科专科护士实践的应用

目的探讨Sandwich教学法在中医骨伤专科护士实践的应用效果。方法选择40名中医骨伤科专科护士学员为研究对象,采用随机数字表法平均分为Sandwich教学法带教组(实验组)和授课为基础的教学法(LBL)带教组(对照组)。培训结束后比较两组学员理论考核、中医个案护理考核和操作考核的成绩,并调查学员对教学效果的评价。结果实验组的理论考核、中医个案护理考核以及操作考核成绩均高于对照组,差异有统计学意义(P<0.05)。与LBL教学法相比,绝大多数学员认为,应用Sandwich教学法能提高辨证施护能力、解决问题能力、思维开放能力、临床管理能力以及人际沟通能力。结论Sandwich教学法在中医骨伤科专科护士的实践教学中效果较好,值得进一步推广应用。

Sandwich联合CBL在中医内科专科护士临床带教的应用

目的观察Sandwich联合案例式教学法(CBL)在中医内科专科护士临床实践教学中的应用效果。方法将32名中医内科专科护士随机分为Sandwich联合CBL教学组(实验组)和讲授式教学法(LBL)组(对照组),各16名。在临床实践结束后,比较两组理论及技能操作成绩的差异性,并调查学员对临床教学效果的满意度。结果实验组的理论及技能操作成绩高于对照组,且病案分析题、中医四诊收集和辨证施护成绩显著优于对照组,差异有统计学意义(P<0.05)。与LBL教学法比较,绝大多数学员认为应用Sandwich联合CBL教学法更能提高自身辨证施护能力、组织协调能力、人际交往能力、思维批判能力以及科研创新能力。结论Sandwich联合CBL教学法更适合中医内科专科护士的临床带教,有利于提高学员的岗位胜任力。

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.

A Modified Principal Component Analysis Method for Honeycomb Sandwich Panel Debonding Recognition Based on Distributed Optical Fiber Sensing Signals

The safety and integrity requirements of aerospace composite structures necessitate real-time health monitoring throughout their service life.To this end,distributed optical fiber sensors utilizing back Rayleigh scattering have been extensively deployed in structural health monitoring due to their advantages,such as lightweight and ease of embedding.However,identifying the precise location of damage from the optical fiber signals remains a critical challenge.In this paper,a novel approach which namely Modified Sliding Window Principal Component Analysis(MSWPCA)was proposed to facilitate automatic damage identification and localization via distributed optical fiber sensors.The proposed method is able to extract signal characteristics interfered by measurement noise to improve the accuracy of damage detection.Specifically,we applied the MSWPCA method to monitor and analyze the debonding propagation process in honeycomb sandwich panel structures.Our findings demonstrate that the training model exhibits high precision in detecting the location and size of honeycomb debonding,thereby facilitating reliable and efficient online assessment of the structural health state.

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。

Sandwich教学法在乳腺外科临床见习教学中的应用

对Sandwich教学法在临床见习教学中的实际应用展开研究与分析。方法 选择我院40例乳腺外科实习生作为本次的试验对象,根据不同带教方法将其分成两组,每组分别20例。结果 两组带教效果比较,观察组较对照组更高,数据存在差异,有统计学意义P<0.05。观察组单选题、名词解释、论述题、分析题各项成绩均优于对照组,组间数据有差异,具有统计学意义P<0.05。观察组理论成绩、实践成绩均优于对照组,差异显著,存在统计学意义P<0.05。结论 将Sandwich教学法应用在我院乳腺外科见习实习生中可提升带教效果及满意度,值得临床应用与推广。

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。

任务驱动联合Sandwich教学法在骨科实习护生带教中的应用

目的探讨任务驱动教学法联合Sandwich教学法在骨科实习护生带教中的应用效果。方法选取2020年6月至2021年8月在广东省中医院骨科实习的59名护生为研究对象,根据不同护理教学方法分为对照组(28名)和试验组(31名)。对照组女24名,男4名,年龄(21.25±0.65)岁,按照常规教学法教学;试验组女28名,男3名,年龄(21.71±0.59)岁,在常规教学基础上进行任务驱动教学法联合Sandwich教学法教学;对比两组学习积极主动性(ALS)及批判性思维能力(CTDI-CV)、理论知识考核成绩、操作实践考核成绩及教学满意度。计量资料采用独立样本t检验,计数资料采用χ^(2)检验。结果入科时,两组ALS评分和CTDI-CV评分比较,差异均无统计学意义(均P>0.05);出科时,试验组ALS评分和CTDI-CV评分均高于对照组[(75.48±6.34)分比(67.18±6.57)分、(284.29±7.69)分比(267.39±9.42)分],差异均有统计学意义(t=4.936、7.578,均P<0.001)。试验组出科理论知识考核成绩和操作实践考核成绩均高于对照组[(88.06±6.53)分比(80.29±8.70)分、(87.68±5.71)分比(78.96±7.09)分],差异均有统计学意义(t=3.910、5.221,均P<0.001)。试验组教学总满意率高于对照组[93.5%(29/31)比75.0%(21/28)],差异有统计学意义(χ^(2)=3.915,P<0.05)。结论将任务驱动教学法联合Sandwich教学法应用于骨科实习护生带教中,可充分调动护生的自主学习积极主动性,强化批判性思维能力,提高专科理论知识水平、操作实践能力及教学满意度。

PCMC联合Sandwich的教学方法探索与实践——以中医皮肤病学为例

为探索中医皮肤病学临床实习中开展PCMC联合Sandwich教学法的教学效果,选择在北京中医药大学东直门医院皮肤科实习的60名2019级学生为研究对象,随机分为观察组和对照组,每组30人。对照组采用传统临床带教;观察组采用医学人文教育融入PCMC联合Sandwich教学模式,问卷调查两组学生的理论水平和实践能力,包括专业知识、临床技能、人文素质和教学满意度等。观察组的理论考核成绩、临床技能、总体临床能力和教学满意度均显著优于对照组(P<0.001)。PCMC和Sandwich两种教学方法优势互补,能够调动医学生的学习积极性,夯实其理论知识,提升临床技能,培养临床思维能力和人文医学素养。