A 1D time-domain method for in-plane wave motions in a layered half-space

A 1D finite element method in time domain is developed in this paper and applied to calculate in-plane wave motions of free field exited by SV or P wave oblique incidence in an elastic layered half-space. First, the layered half-space is discretized on the basis of the propagation characteristic of elastic wave according to the Snell law. Then, the finite element method with lumped mass and the central difference method are incorporated to establish 2D wave motion equations, which can be transformed into 1D equations by discretization principle and explicit finite element method. By solving the 1D equations, the displacements of nodes in any vertical line can be obtained, and the wave motions in layered half-space are finally determined based on the characteristic of traveling wave. Both the theoretical analysis and the numerical results demonstrate that the proposed method has high accuracy and good stability.

A Prediction Method for In-Plane Permeability and Manufacturing Applications in the VARTM Process

VARTM (Vacuum Assisted Resin Transfer Molding) is a popular method for manufacturing large-scaled, single-sided mold composite structures, such as wind turbine blades and yachts. Simulation to find the proper infusion scenario before manufacturing is essential to avoid dry spots as well as incomplete saturation and various fiber weaves with different permeability affect numerical simulation tremendously. This study focused on deriving the in-plane permeability prediction method for FRP (Fiber Reinforced Plastics) laminates in the VARTM process by experimental measurements and numerical analysis. The method provided an efficient way to determine the permeability of laminates without conducting lots of experiments in the future. In-plane permeability imported into the software, RTM-Worx, to simulate resin flowing pattern before the infusion experiments of a 3D ship hull with two different infusion scenarios. The close agreement between experiments and simulations proved the correctness and applicability of the prediction method for the in-plane permeability.

Optical simulation of in-plane-switching blue phase liquid crystal display using the finite-difference time-domain method

The finite-difference time-domain method is used to simulate the optical characteristics of an in-plane switching blue phase liquid crystal display.Compared with the matrix optic methods and the refractive method,the finite-difference timedomain method,which is used to directly solve Maxwell＇s equations,can consider the lateral variation of the refractive index and obtain an accurate convergence effect.The simulation results show that e-rays and o-rays bend in different directions when the in-plane switching blue phase liquid crystal display is driven by the operating voltage.The finitedifference time-domain method should be used when the distribution of the liquid crystal in the liquid crystal display has a large lateral change.

Amplification of in-plane seismic ground motion by group cavities in layered half-space (Ⅱ): with saturated poroelastic soil layers

As the continuation study on amplification of in-plane seismic ground motion by underground group cavities in layered half-space, this study extends to the case of poroelastic half-space with dry poroelastic and saturated poroelastic soil layers. The influence of poroelastic layers on the amplification of seismic ground motion is studied both in frequency domain and time domain using indirect boundary element method （IBEM）. It is shown that for the example of a saturated poroelastic site in Tianjin under the excitation of Taft wave and E1 Centro wave, the amplification of seismic ground motion in poroelastic case is slightly smaller than that in the elastic case, and the amplification of PGA （peak ground acceleration） and its PRS （peak response spectrum）.. can be increased up to 38.8% and 64.6%; the predominant period of response spectra in poroelastic case becomes shorter to some extent compared with that in the elastic case. It is suggested that the effect of underground group cavities in poroelastic half-space on design seismic ground motion should be considered.

Amplification of in-plane seismic ground motion by group cavities in layered half-space (Ⅰ)

Amplification of in-plane seismic ground motion by underground group cavities in layered half-space is studied both in frequency domain and time domain by using indirect boundary element method （IBEM）, and the effect of cavity interval and spectrum of incident waves on the amplification are studied by numerical examples. It is shown that there may be large interaction between cavities, and group cavities with certain intervals may have significant amplification to seismic ground motion. The amplification of PGA （peak ground acceleration） and its PRS （peak response spectrum） can be increased up to 45.2% and 84.4%, for an example site in Tianjin, under the excitation of Taft wave and E1 Centro wave; and group cavities may also affect the spectra of the seismic ground motion. It is suggested that the effect of underground group cavities on design seismic ground motion should be considered.

Thermal buckling and postbuckling of FGM circular plates with in-plane elastic restraints

Based on von Karman＇s plate theory, the axisymmetric thermal buckling and post-buckling of the functionally graded material （FGM） circular plates with in- plane elastic restraints under transversely non-uniform temperature rise are studied. The properties of the FGM media are varied through the thickness based on a simple power law. The governing equations are numerically solved by a shooting method. The results of the critical buckling temperature, post-buckling equilibrium paths, and configurations for the in-plane elastically restrained plates are presented. The effects of the in-plane elastic restraints, material property gradient, and temperature variation on the responses of thermal buckling and post-buckling are examined in detail.

In-Plane Elastic Stability of Arches under a Radial Concentrated Load

This paper is concerned with the in-plane elastic stability of arches subjected to a radial concentrated load. The equilibrium equation for pin-ended circular arches is established by using energy method, and it is proved that the axial force is nearly a constant along the circumference of the circular arches. Based on force method, the equation for the primary eigen function is derived and solved, and the approximate analytical solution of critical instability load is obtained. Numerical examples are given and discussed.

超声引导下肉毒毒素注射对痉挛型脑瘫儿童运动功能的疗效

目的:探究痉挛型脑瘫儿童治疗中超声引导下肉毒毒素注射对患儿运动功能的影响。方法:选取2021年6月~2022年5月郴州市第一人民医院收治的2~6岁双下肢痉挛的脑瘫患儿80例作为研究对象,依据定位技术分为超声引导下肉毒毒素注射组(超声引导组)、徒手肌肉定位肉毒毒素注射组(徒手肌肉组)各40例。统计分析两组踝关节被动屈曲角度、踝背伸角、内收肌角、腘窝角、踝跖屈肌群肌张力、踝跖屈肌群痉挛程度、躯干与下肢运动功能、粗大运动功能、日常生活能力、不良反应发生情况及家长满意度。结果:超声引导组患儿的左侧、右侧踝关节被动屈曲角度均小于徒手肌肉组(P<0.05),踝背伸角、内收肌角、腘窝角均大于徒手肌肉组(P<0.05);超声引导组患儿的改良Ashworth评分(MAS)、综合痉挛量表(CSS)评分均低于徒手肌肉组(P<0.05),MOA评分、GMFM D区与E区评分、MBI评分均高于徒手肌肉组(P<0.05)。超声引导组患儿的不良反应发生率低于徒手肌肉组(χ^(2)=4.507,P<0.05);超声引导组患儿家长满意度高于徒手肌肉组,差异均有统计学意义(χ^(2)=7.440,P<0.05)。结论:超声引导下较徒手肌肉定位法肉毒毒素注射在痉挛型脑瘫儿童治疗中能够改善患儿运动功能。

手绘效果图表现速成法探析

手绘效果图是设计师用来表达设计意图、传达设计理念和设计思想的一种设计语言,是设计的组成部分,用图解思考即综合多元的感性思维与理性思维方法,是从意到图的设计构思与设计实践的升华。本文探讨,将复杂多种的表现技法浓缩成几种有规律的表现技法。在训练方法上采用了分解训练与综合训练、感性与理性的学习方法。从而在较短的时间里掌握好手绘效果图快速表现技法。

大花鸟 新境界——方楚雄和吉瑞森花鸟画艺术浅议

写意花鸟画的发展与突破在中国画中一直是一个难题。中国画是以线为主的艺术创作形式,线有其独特的审美价值,在写意花鸟画中线的作用更显突出。方楚雄、吉瑞森把工笔花鸟画中的双勾造型运用到写意花鸟画之中,并把线的作用发挥到了极致,形成了新的写意花鸟画创作样式,有明显的风格趋向,极具学术价值,为写意花鸟画的创作提供了新的技术支持,是真正的"大花鸟、新境界"。

写意油画意境美的表现

中国传统绘画追求意境美,写意油画依托于中国传统美学,合水墨精神以营造意境为其精神支柱。几代艺术家们在写意油画意境美表现上经过自己不懈努力,寻觅自我阐释的语言,以及写意油画意境美的表现方法。归纳起来主要有:1、景物虚实相生,追求气韵生动。2、研习传统笔法,融入肌理效果3、研习传统笔法,融入肌理效果4、运用传统构图形式。

国画课中如何使学生作品呈现东西方绘画因素的完美糅合

中国画作为绘画的主要画种,在我国美术界有着特殊的历史地位。中国画的观察与绘画方法与西方的绘画因素有着许多相同之处,教师要巧妙的使用教学方法,使学生在学习的过程中完美的糅合东西方的绘画因素,抒发作者的思想感受,展现中国画的绘画魅力。

论徐渭的水墨大写意花鸟画

明代大画家徐渭独创的大写意花鸟画,在我国绘画艺术史上具有深远的影响。其画主要特点有三;一是集绘画、书法和文学于一体,属典型的文人画;二是采用了酣畅淋漓的泼墨法;三是采用了豪放纵逸的大写意笔法。

论'99昆明世界园艺博览会中国馆设计的“写意”手法

本文从 ' 99昆明世界园艺博览会中国馆的外观、造型、色彩、庭院布局及展室设计等方面 ,探讨了写意手法的“意境”运用。

Distinct Element Modelling of Unreinforced Masonry Wall Under Seismic Loads with and without Cable Retrofitting

To retrofit and strengthen existing unreinforced masonry (URM) structures to resist the potential earthquake damages has become an important issue in Australia. In order to secure the performance of URM under seismic loading in the future, a research project was carried out aimed at developing a simple and high strength seismic retrofitting technique for masonry structures. A series of experimental testing on URM walls retrofitted with an innovative technique by cable system have been conducted. The results indicated that both the strength and ductility of the tested speci-mens were significantly enhanced with the technique. An analytical model which is based on Dis-tinct Element Method (DEM) has also been developed to simulate the behaviour of URM walls be-fore and after retrofitting. The model is then further developed by applying a seismic wave to the wall to simulate the wall behavior under earthquake loads before and after retrofitting.

螺旋CT三维重建辅助胸腰椎骨折椎弓根钉置入的准确性评价

目的探讨螺旋CT三维重建辅助胸腰椎骨折椎弓根螺钉置入的准确性。方法选取2015年3月~2018年3月在我院因胸腰椎骨折行椎弓根螺钉置入的患者120例,随机分为三维辅助组(n=60)和徒手置钉组(n=60),三维辅助组利用CT三维重建图像辅助置入椎弓根螺钉,徒手置钉组应用解剖标志法结合透视定位下行椎弓根螺钉置入;比较两组置钉准确性、置钉时间、置钉出血量、并发症及术前术后日本骨科协会(JOA)评分。结果 120例患者共置钉769枚,优良置钉708枚(92.07%),其中三维辅助组(387枚)置钉优良率为95.09%,明显高于徒手置钉组(382枚)的87.86%(P<0.05)。与徒手置钉组相比,三维置钉组钉道准备时间、置钉出血量均明显增加(P<0.05)。三维辅助组并发症发生率明显低于徒手置钉组(P<0.05),术后3个月及6个月JOA评分均明显高于徒手置钉组(P<0.05)。结论螺旋CT三维重建辅助胸腰椎骨折椎弓根螺钉置入能够有效提高置钉准确性及安全性,但会增加操作时间及置钉出血量。

高频超声引导介入治疗在肘部囊肿中的应用价值

目的分析肘部囊肿开展高频超声引导介入治疗的作用。方法选择深圳市龙华区人民医院和深圳市龙岗中心医院收治的60例肘部囊肿病患为研究主体,研究时间为2020年7月-2021年8月。全部病患在进入医院后均实施高频超声检查肘部细微结构改变,了解肌肉肌腱、四周血管和神经走行情况。同时在高频超声引导下,依据肘部囊肿不同位置,制定相应穿刺入路,徒手平面内法穿刺针刺入靶目标抽吸囊液,之后使用维生素B12和地塞米松进行冲洗,并注入3~5mL浓度为35μg/mL的臭氧。分析肘部囊肿高频超声检查情况;分析超声引导下介入治疗效果;分析疾病复发率、穿刺一次治愈率、穿刺两次治愈率。结果在60例病患中,19例为尺骨鹰嘴滑囊囊肿,10例为桡骨小头环韧带囊肿,9例为肱二头肌桡骨囊囊肿,4例肘骨间滑囊囊肿,9例为副韧带损伤囊肿,6例为腱鞘囊肿以及3例为内、外上髁滑囊囊肿。超声引导下介入治疗总有效率是90.00%。疾病复发率是1.67%,穿刺一次治愈率为83.33%,穿刺两次治愈率是16.67%。结论肘部囊肿开展高频超声检查能够有效诊断疾病,在超声引导下进行介入治疗效果良好,疾病复发率低,穿刺一次治愈率高,可发挥良好的诊断以及治疗作用。

Near-zero Poisson's ratio and suppressed mechanical anisotropy in strained black phosphorene/SnSe van der Waals heterostructure:a first-principles study

Black phosphorene(BP)and its analogs have attracted intensive attention due to their unique puckered structures,anisotropic characteristics,and negative Poisson’s ratio.The van der Waals(vdW)heterostructures assembly by stacking different materials show novel physical properties,however,the parent materials do not possess.In this work,the first-principles calculations are performed to study the mechanical properties of the vdW heterostructure.Interestingly,a near-zero Poisson’s ratio ν_(zx)is found in BP/SnSe heterostructure.In addition,compared with the parent materials BP and SnSe with strong in-plane anisotropic mechanical properties,the BP/SnSe heterostructure shows strongly suppressed anisotropy.The results show that the vdW heterostructure has quite different mechanical properties compared with the parent materials,and provides new opportunities for the mechanical applications of the heterostructures.

Chemical vapor deposition synthesis and Raman scattering investigation of quasi-one-dimensional ZrS_(3)nanoflakes

Quasi-one-dimensional ZrS_(3)nanoflakes attract intense interest attributed to their superior electrical and optical anisotropy,stemming from the low symmetry in the crystal structure.However,the conventional chemical vapor transport method for synthesizing bulk ZrS_(3)is limited by morphology and size controllability.It is highly desirable to propose a facile way to precisely synthesize ZrS_(3)nanoflakes.In this work,the chemical vapor deposition method is proposed as a feasible way to synthesize ZrS_(3)nanoflakes.The effects of various substrates and temperatures on ZrS_(3)synthesis have been investigated.For the as-grown ZrS_(3),good crystallinity is confirmed with X-ray diffraction and transmission electron microscopy.The structure and interlayer coupling are investigated with Raman scattering spectroscopy.The strong in-plane anisotropy and interlayer coupling of the ZrS_(3)nanoflakes are illustrated with angle-resolved Raman spectroscopy and temperature-dependent Raman characterization,respectively.This study demonstrates a feasible way for the synthesis of transition metal trisulfides,which may shed new light on the research of other two-dimensional anisotropic transition metal materials.

Buckling and post-buckling behavior of titanium alloy stiffened panels under shear load

Titanium alloy has been increasingly applied in aviation industry due to its superior performance. However, the titanium alloy structures are less studied. This work investigates the structural behavior of Ti6Al4V titanium alloy stiffened panels under in-plane shear load by experiments and numerical analysis. After the shear tests, the buckling instability, the post-buckling process and the failure mechanism of the specimen were obtained. The Finite Element(FE) models were established with the subsequent validation verification. A parametric analysis was implemented to study the influence of stringer thickness and stringer height on the behavior of the stiffened panels. The results show that after the initial local buckling on the skin, the buckling mode jumps several times with the increase of load. The stringers twist when the load reaches a certain level, and finally the structure damages due to the plastic deformation and the global buckling. The shear clip has little effect on the buckling and failure loads. Compared to the relatively large effect on the buckling load, the influence of the stringer thickness and stringer height on the failure load is neglectable.According to the parametric analysis, the stringer thickness influences the final buckling mode and failure mode, while the stringer height affects the buckling mode transformation.