Modeling,analysis,and simulation of X-shape quasi-zero-stiffness-roller vibration isolators

Existing quasi-zero stiffness(QZS)isolators are reviewed.In terms of their advantages,a novel X-shape QZS isolator combined with the cam-roller-spring mechanism(CRSM)is proposed.Different from the existing X-shape isolators,oblique springs are used to enhance the negative stiffness of the system.Meanwhile,the CRSM is used to eliminate the gravity of the loading mass,while the X-shape structure leaves its static position.The existing QZS isolators are demonstrated and classified according to their nonlinearity mechanisms and classical shapes.It is shown that the oblique spring can realize negative stiffness based on the simplest mechanism.The X-shape has a strong capacity of loading mass,while the CRSM can achieve a designed restoring force at any position.The proposed isolator combines all these advantages together.Based on the harmonic balance method(HBM)and the simulation,the displacement transmissibilities of the proposed isolator,the X-shape isolators just with oblique springs,and the X-shape isolators in the traditional form are studied.The results show that the proposed isolator has the lowest beginning isolation frequency and the smallest maximum displacement transmissibility.However,it still has some disadvantages similar to the existing QZS isolators.This means that its parameters should be designed carefully so as to avoid becoming a bistable system,in which there are two potential wells in the potential energy curve and thus the isolation performance will be worsened.

TRANSITIONS AND MODRPHOLOGY OF MAIN-CHAIN LIQUID CRYSTALLINE POLYMERS WITH X-SHAPED MESOGENS

The transitions and morphology of a series of main-chain liquid crystalline polymer with X-shaped mesogens were studied by means of DSC,SALS and polarizing microscopy techniques. Aneven-odd effect was observed for samples with different size of the substituents on the mesogenends. The isotropization process was similar to that of main-chain polymers with rod-likemesogens. No crystallization was detected for specimens cooling down from their isotropic meltstate. However two of the samples may crystallize in cooling process directly from the liquidcrystalline state.

SYNTHESIS OF MAIN CHAIN LIQUID CRYSTALLINE COPOLYESTERS WITH X-SHAPED TWO-DIMENSIONAL MESOGENIC UNIT AND CROWN ETHER CYCLE

A novel series of main chain liquid crystalline copolyesters with X-shaped two-dimensional mesogenic unit and crown ether cycle of cis-4,4＇-bis（4-hydroxyphenylazo） dibenzo-18-crown-6 was prepared via solution condensation polymerization from 4,4＇-（a;arhexanedioyloxy） dibenzoyl dichloride （MI）, 2,5-bis（p-octyloxybenzoyloxy） hydro-quinone （M2） and cis-4,4＇-bis（4-hydroxyphenylazo） dibenzo-18-crown-6 （M3）. Monomer MI was synthesized by esterification and substitution of adipoyl chloride with p-hydroxybenzoic acid, monomer M2 was synthesized by esterfication and reduction reaction of 2,5-dihydroxybenzoquinone and p-octanoxybenzoyl chloride and monomer M3 was synthesized by diazotization and coupling reaction of cis-diaminodibenzo-18-crown-6 with phenol. The molecular weights of copolyesters are not high, and the intrinsic viscosity [η] of copolyesters ranges from 0.25-0.35. The monomers＇ structures were identified by using elemental analysis, IR, UV, ^1H-NMR, MS, etc. All the copolyesters are yellowish powders and insoluble in THF and CHC13 at room temperature except cPg. The properties of copolyesters were investigated by using GPC, [η] , DSC, TG, WAXD and POM. It was found that all the copolyesters entered into liquid crystal phase when they were heated to above their melting temperature （Tin）. The typical smectic and nematic phase texture can be observed on POM. Their mesophase transition temperature and thermal stability change regularly with varying the content of cis-4,4＇-bis（4-hydroxyphenylazo） dibenzo-18-crown-6 unit in the copolyesters.

SYNTHESIS AND CHARACTERIZATION OF MAIN CHAIN AROMATIC LIQUID CRYSTAL COPOLYESTERS WITH X-SHAPED AND ROD-SHAPED MESOGENIC UNITS

A series of main chain liquid crystal aromatic copolyesters with X-shaped and rod-shaped mesogenic units were synthesized via solution condensation polymerizations of 4,4'-(alpha,omega-octanedioyloxy)-dibenzoyl dichlorides with 2,5-bis(p-octanoxy benzoyloxy)-hydroquinone and diphenol. All of the copolyesters showed thermotropic liquid crystalline behaviors through observations using DSC, polarized microscopy and X-ray diffraction. The melting point (T-m) and the isotropization temperature (T-i) change regularly with varying the content of diphenol unit in the copolymers.

The review of clinical application of X-shaped balance acupuncture therapy for joint pain and activity disorder

Musculoskeletal diseases such as neck, shoulder, back and leg pain are ext remely common in clinic. Diseases of the joints of the ext remi ti es, especially sputum, wr ist spr ains, and periarthritis of the shoulders, and even lumbar disc herniation, use X-shaped balance acupuncture therapy to relieve pain and improve motor function. The method of obtaining acupoints is simple and easy to operate. Many of clinical comparison shows that this therapy is simple to conventional acupuncture and moxibustion in the treatment of local pain and joint diseases. This review concluded the advantaged about the X-shaped balance acupuncture therapy and it worth to clinical promotion.

Seismic Behavior of Specially Shaped Column Joints with X-Shaped Reinforcement

To investigate the seismic behavior of specially shaped column joints with X-shaped reinforcement,two groups of specimens with or without X-shaped reinforcement in joint core region were tested under constant axial compression load and low reversed cyclic loading,which imitated low to moderate earthquake force.The seismic behavior of specially shaped column joints with X-shaped reinforcement in terms of bearing capacity,displacement,ductility,hysteretic curve,stiffness degradation and energy dissipation was studied and compared to that without Xshaped reinforcement in joint core region.With the damage estimation model,the accumulated damage was analyzed.The shearing capacity formula of specially shaped column joints reinforced by X-shaped reinforcement was proposed with a simple form.The test results show that X-shaped reinforcement is an effective measure for improving the seismic behavior of specially shaped column joints including deformation behavior,ductility and hysteretic characteristic.All specimens were damaged with gradual stiffness degeneration.In addition,X-shaped reinforcement in the joint core region is an effective way to lighten the degree of cumulated damage.The good seismic performance obtained from the specially shaped column joint with X-shaped reinforcement can be used in engineering applications.The test value is higher than the calculated value,which indicates that the formula is safe for the design of specially shaped column joints.

X形软钢阻尼器延性断裂的试验研究与数值模拟

为了研究X形软钢阻尼器在大变形状态下的耗能性能和损伤演化规律,设计了6组试件进行单向和循环荷载作用下延性断裂的试验研究,分析了软钢阻尼器的破坏过程和滞回曲线。采用Lemaitre-Chaboche混合强化模型,分别对各工况下包含与不包含基于应力三轴度的钢材微观损伤模型的软钢阻尼器进行了精细的有限元模拟。对比有限元模拟结果和试验结果,分析结果表明,颈部为X形耗能软钢阻尼器的薄弱位置,最容易发生集中损伤甚至破坏。考虑钢材损伤准则的有限元模拟的荷载-位移曲线与试验结果更加吻合,能够表征软钢阻尼器的承载力与刚度退化现象,并能较为准确地预测软钢阻尼器的损伤演化过程和断裂破坏位置。

基于循环孔洞扩张模型的X型圆管节点超低周疲劳寿命预测

海洋工程钢结构在服役过程中,受风、浪、流或地震等极端循环载荷的影响,易发生超低周疲劳断裂破坏,造成人员伤亡及财产损失,因此超低周疲劳断裂分析及寿命预测对于海工结构安全性评估至关重要。然而,现阶段基于累积损伤理论提出的多种超低周疲劳寿命预测模型无法对多尺度节点实现统一预测,造成了实际工程应用的不便。因此文中基于循环孔洞扩张模型开展X型圆管节点超低周疲劳寿命预测。首先,开发了基于循环孔洞扩张模型的VUSDFLD程序,实现ABAQUS与FORTRAN子程序联合应用,利用有限元分析验证循环孔洞扩张模型在X型圆管节点超低周疲劳断裂分析中的有效性;其次,根据多组X型圆管节点超低周疲劳断裂有限元分析结果,在宏观层面提出了一种基于Manson-Coffin公式的超低周疲劳寿命预测公式;最后,依据Miner理论,将适用于等幅加载的超低周疲劳寿命公式扩展至变幅加载情况,验证了多种节点尺寸下超低周疲劳公式的适用性,为工程应用提供了理论依据。

Constructal entransy dissipation rate minimization for X-shaped vascular networks

Combining with entransy theory, constructal designs of the X-shaped vascular networks(XSVNs) are implemented with fixed total tube volumes of the XSVNs. The entransy dissipation rates(EDRs) of the XSVNs are minimized, and the optimal constructs of the XSVNs are derived. Comparison of the optimal constructs of the XSVNs with two optimization objectives(EDR minimization and entropy generation rate(EGR) minimization) is conducted. It is found that when the dimensionless mass flow rate(DMFR) is small, the optimal diameter ratio of the elemental XSVN derived by EDR minimization is different from that derived by EGR minimization. For the multilevel XSVN, when the DMFR is 100, compared the XSVN with the corresponding H-shaped vascular network(HSVN), the dimensionless EDRs of the elemental, second and fourth order XSVNs are reduced by 26.39%, 15.34% and 9.81%, respectively. Compared with the entransy dissipation number(EDN) of the second order XSVN before angle optimization, the EDN after optimization is reduced by 26.15%, which illustrates that it is significant to conduct angle optimization of the XSVN. Entransy theory is applied into the constructal design of the vasculature with heat transfer and fluid flow in this paper, which provides new directions for the vasculature designs.

RELATIONSHIP OF FIRST STEP HEIGHT,STEP SLOPE AND CAVITY IN X-SHAPED FLARING GATE PIERS

The energy dissipation of X-shaped flaring gate piers ahead of a stepped spillway was adopted in the Suofengying Hydroplant. Under the circumstance that the first step is higher than others, at the step surface an aerated cavity occured behind piers. The interaction of the weir head, the elevation difference between crest and chamber outlet, the first step height, the slopes of weir end and step, and the size of cavity, was investigated, the expression was derived to characterize their relationship, and the corresponding curves were plotted. The comparison of the calculated and simulated results with the measured data was performed. When the slopes of step and weir end are equivalent, the relative height difference between the first and second steps becomes the main factor influencing the aerated cavity. These findings may be useful in practical applications.

引排结合多工况泵站总体布置型式探讨

泵站工程从功能上来说可分为引水和排涝两大类。某些平原圩区泵站枢纽工程要求同时具备机排、机引、自排、自引多种工况调度功能,相对于传统泵站,其具有节省投资、减少占地、管理集中等优点。引排结合泵站的设计要点和难点在于总体布置型式的选择及运行调度方案的确定。文章结合阜阳市某水系连通项目,对引排结合多工况泵站的几种总体布置方案进行了介绍及分析,设计方案均合理可行,可为其他相关的引排结合泵站设计提供思路和借鉴。

Characterization of x-shaped nanoaperture antenna arrays operating in mid-infrared regime

The characterization of x-shaped antenna arrays operating in the mid-infrared is proposed. An equivalent circuit model for the resonant characteristic of the x-shaped nanoaperture antenna arrays is also included. In order to understand the resonance behavior of the structure, a detailed study of the field-enhancement capabilities and light transmission characteristics of the structure is proposed. In the experimental stud- ies, the transmission characteristics of the periodic x-apertures are analyzed by varying the geometrical dimensions. Consequently, it is observed that the periodic subwavelength x-apertures show extremely high near-field optical resolution and enhanced transmission compared with the other nm-sized apertures.

X形汽车吊具的运动性能及力学性能分析

为满足X形汽车吊具多体运动系统的工作性能和安全性能,对其进行数字化设计,建立了三维装配模型,并导入ADAMS软件中构建动力学模型;模拟了常规运行工况和单侧电机故障工况下的运动过程,得到位移、速度和加速度曲线,以及铰孔接触力曲线,确定了铰孔受力最大时X形机构的运动位置;采用有限元分析法对该位置在常规运行工况、单侧电机故障工况和一侧外力干扰工况下的力学性能进行分析。结果表明:X形汽车吊具在各工况下均满足强度和变形要求,进而验证了结构的力学性能,为设计方案的进一步迭代与优化提供参考。

颈椎前路X形椎体次全切除融合内固定术治疗双节段颈椎病的疗效分析

目的:探讨颈椎前路X形椎体次全切除融合内固定术(anterior cervical X-shape-corpectomy and fusion,ACXF)治疗双节段颈椎病的临床疗效。方法:回顾性分析2019年1月~2020年12月间在我院骨科行ACXF治疗的双节段颈椎病患者的临床资料,并与同期行颈椎前路椎体次全切除融合固定术(anterior cervical corpectomy and fusion,ACCF)治疗的双节段颈椎病患者进行比较。收集两组患者的基线信息、手术时间、出血量及住院时间,术前和术后即刻、3个月、6个月及1年时行日本骨科学会(Japanese Orthopaedic Association,JOA)评分、疼痛视觉模拟评分(visual analogue scale,VAS),术前和术后3个月、术后6个月及术后1年行颈椎功能障碍指数(neck disability index,NDI)评估;测量ACXF组术中前方截骨距离以及两组患者术前和术后不同随访时间点的颈椎整体曲度、手术节段脊柱功能单位(functional spine unit,FSU)活动度及高度、后方减压范围、骨性椎管前后径(anterior-posterior diameter,APD)和面积(spinal canal area,SCA)等影像学参数,评估椎间融合情况,同时记录患者相关并发症。结果:共纳入46例患者,其中17例行ACXF,29例行ACCF。所有患者手术均顺利完成,ACXF组患者手术时间、出血量和住院时间分别为144.71±30.44min、109.41±55.51ml和8.35±1.46d,ACCF组分别为155.17±27.86min、126.90±51.55ml和12.03±3.34d,两组手术时间和出血量无统计学差异,ACXF组住院时间显著性少于ACCF组(P<0.001)。两组患者术后即刻、3个月、6个月和1年时的JOA评分、VAS评分及术后3个月、6个月和1年时的NDI均较术前显著性改善,两组同时间点的JOA评分、VAS评分和NDI均无显著性差异(P>0.05)。两组术前颈椎曲度无显著性差异,术后即刻、6个月和1年时ACXF组显著性大于ACCF组(P<0.05)。两组术后各时间点的FSU活动度与术前比较均显著性降低(P<0.01),两组同时间点比较均无显著性差异(P>0.05)。两组术后即刻FSU高度较术前显著性增加(P<0.01),ACXF组术后3个月与术前比较有显著性差异(P<0.05);两组同时间点比较均无显著性差异(P>0.05)。ACXF组后方减压范围为11.66±1.31mm,显著性小于ACCF组(16.32±2.00mm)(P<0.001);两组术后各时间点的骨性椎管APD和SCA均术前显著性增大,ACXF组术后各时间点的骨性椎管SCA及术后1年时的APD小于同时点ACCF组(P<0.05)。两组术后3个月、6个月、1年时的融合率均无显著性差异(P>0.05),ACXF组内置物下沉的发生率分为别17.65%(3/17)、23.53%(4/17)及23.53%(4/17),均显著性低于同时间点ACCF组(P<0.05)。ACXF组1例患者在术后出现轻度吞咽困难,予以保守治疗后症状明显缓解,出院时症状消失;无脑脊液漏发生。ACCF组术后出现4例吞咽困难,行康复训练,出院时症状明显好转,术后3个月随访时症状消失;3例患者发生脑脊液漏,予以延迟拔管等对症治疗,出院时治愈。结论:ACXF可以显著改善颈椎病患者的临床症状及神经功能,临床疗效与ACCF一致;且在保证充足减压范围的情况下能够进一步降低术后内置物沉降的发生,是治疗合并椎体段狭窄的双节段颈椎病的一种术式选择。

Vibration isolation performance analysis of a bilateral supported bio-inspired anti-vibration control system

To achieve better anti-vibration performance in a low frequency region and expand the range of vibration isolation,a bilateral supported bio-inspired anti-vibration(BBAV)structure composed of purely linear elements is proposed,inspired by the motion form of bird legs and the nonlinear extension and compression of muscles and tendons.The kinematic relations and nonlinear dynamic model considering vertical and rotational vibrations are established.The loading capacity and equivalent stiffness are investigated with key parameters.The amplitude-frequency characteristics and force transmissibility are used to evaluate the stability and anti-vibration performance with the effects of the excitation amplitude,rod length,installation angle,and spring stiffness.The results show that the loading requirements and resonant characteristics of the BBAV structure are adjustable,and superior vibration isolation performance can be achieved readily by tuning the parameters.The X-shaped vibration structure is sensitive to the spring stiffness,which exhibits a wider vibration isolation bandwidth with smaller spring stiffness.Besides,depending on the parameters,the nonlinear behavior of the BBAV system can be interconverted between the softening type and the hardening type.The theoretical analysis in this study demonstrates the advantages and effectiveness of the vibration isolation structure.

抛物线型柱面弯晶谱仪在Z箍缩软X射线辐射能谱测量中的应用

针对Z箍缩软X射线辐射能谱测量,采用双通道拼接方式实现量程搭接,设计了一种抛物线型柱面弯晶谱仪。介绍了基于平行光正入射的解谱方法,分析了平行光斜入射及点源入射条件下对能谱测量范围的影响,并提出了对应的能量修正方法。在“强光一号”装置上开展验证实验,测量了钼丝阵等离子体2~6 keV范围的辐射谱,给出了辐射线谱形态及相对强度,与理论计算及此前同类实验结果相比,谱线能量及形态一致性较好,验证了谱仪设计及解谱算法的正确性。基于辐射线谱相对强度测量结果,计算了钼丝阵等离子体电子温度约为1 200 eV。

消隔组合X型减振器设计与动力学分析

本文将一种X型结构与线性弹簧阻尼减振器相结合构成一种兼具消振和隔振性能的新型X型减振器.基于拉格朗日方法建立单自由度线性振子耦合消隔组合X型减振器系统的动力学方程,应用谐波平衡法得到系统稳态响应的近似解析解,并通过Runge-Kutta法得到系统的数值解验证解析解的正确性.讨论了不同的基础激励下新型X型减振器对系统的响应幅值以及位移传递率的减振效果.此外,分析了不同参数对系统的幅频响应曲线以及位移传递率的影响.研究结果表明,新型X型减振器不仅可以将线性刚度转化为非线性刚度,还可以为系统提供负刚度,拥有优秀的消振和超低频隔振性能.

洮河大桥主桥桥式方案研究

研究目的:洮河大桥为兰合铁路的控制性工程,大桥位于高烈度地震高山峡谷区,峡谷呈典型的“U”字形,峡谷两岸坡面陡立,基岩裸露,桥梁方案需结合地形条件、地质条件、施工条件、结构安全、景观效果、工程造价等因素综合考虑研究。根据通航要求、地形条件和景观效果等确定采用主跨220 m的钢筋混凝土拱桥方案,进而对钢筋混凝土箱形板拱采用劲性骨架法施工和钢筋混凝土X形拱桥采用悬臂浇筑法施工分别进行研究分析,确定钢筋混凝土箱形板拱和钢筋混凝土X形拱桥构造尺寸,并计算拱肋应力、刚度、稳定性、动力特性及拱座应力是否满足规范要求。研究结论:(1)通过对洮河大桥主桥两个拱桥方案进行综合比较,拱肋应力、刚度、稳定性、动力特性及拱座应力均满足规范要求;(2)钢筋混凝土板拱采用劲性骨架法施工很好地解决了施工中刚度和稳定性的问题,施工经验丰富,技术成熟,安全性好,为国内拱桥普遍使用的施工方法;(3)本文研究对高烈度地震区、高山峡谷区的大跨度拱桥设计具有借鉴意义。

装配式可调间距的X形抗滑动轨枕研究

为增强轨枕的工作性能和减少钢筋混凝土用量,对传统条形轨枕进行结构优化,提出预制装配式X形可调间距轨枕,并对X形轨枕的结构特点、制作流程、轨道维护和钢筋混凝土用量进行分析。同时,建立三维有砟轨道有限元数值模型,对比循环荷载作用下传统轨枕与X形轨枕的竖向、侧向位移和轨枕应力分布。预制装配式X形轨枕由上、下轨枕两部分拼装组成,轨枕间距设计成600,700,800 mm三档,可在自研的X形轨枕制作模具中直接浇筑成形;相同轨枕间距下,铺设X形轨枕每千米混凝土用量相较于Ⅲa型轨枕减少16.7%,钢筋用量减少2.6%;当X形轨枕间距从600 mm增至700,800 mm时,每千米所需铺设的轨枕根数分别减少14.8%和25.5%。模拟结果表明,相较于传统轨枕,采用X形轨枕的轨道竖向沉降减少了5.8%,侧向位移减少了8.4%。新型X形轨枕具有降低道床沉降和促进碳减排的潜能。

一种适宜机械化操作的桃树“X”形栽培模式

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