前牙种植体失败的危险因素分析黄丰;何健慧;欧阳颖【摘要】目的比较前牙延期和即刻负重种植体的2年生存率,探讨与种植失败相关的危险因素。
方法收集2012年7月—2015年7月期间进行的前牙种植患者126名,共植入种植体210颗,随访2年以上。
使用Lo?gRank Test和Cox回归分析进行单因素及多因素生存分析,明确即刻负重及延期负重种植体失败的危险因素。
结果前牙延期负重组和即刻负重组种植体2年生存率分别为96.3%和89.0%,两者差异有统计学意义(P<0.05),延期负重种植体具有更高的2年生存率。
生存分析结果提示延期和即刻负重种植失败的危险因素均为上颌骨种植和种植期间吸烟。
结论前牙即刻负重种植存在较高风险,上颌前牙区种植以及患者种植期间吸烟可能引起种植失败。
【期刊名称】《口腔疾病防治》【年(卷),期】2018(026)004【总页数】4页(P250-253)【关键词】即刻负重;前牙种植;危险因素;上颌骨种植;吸烟【作者】黄丰;何健慧;欧阳颖【作者单位】[1]珠海市口腔医院种植科,广东珠海519000;;[1]珠海市口腔医院种植科,广东珠海519000;;[2]中山大学光华口腔医学院·附属口腔医院口腔颌面外科,广东广州510060;【正文语种】中文【中图分类】R782.12传统观点认为种植体植入骨内3～6个月是创口愈合和骨整合的最佳时期，在此期间内不建议接受负重［1-3］。
此观点是基于种植体在愈合期间负重会增加种植体垂直或水平向受力从而导致种植体产生动度，其后果是异常愈合或纤维组织包裹种植体，而不是骨整合所需的骨形成［4-5］。
随着种植技术的发展，此观点逐渐受到质疑。
部分学者主张植入种植体的同时立即负重（植入72 h内修复牙冠使其负重），他们认为种植体负荷只要控制在一定范围内，其微动度可促进种植体的骨整合，因此无需经过完全无负荷的种植愈合期，甚至在负重条件下的骨整合效果更优于无负重条件［6-7］。
多分支管道油气爆炸特性大涡模拟LIU Chong;DU Yang;ZHANG Peili;MENG Hong;LI Shu;SUN Xiaokang【摘要】为了研究油库常见的分支结构空间内发生油气爆炸时火焰和压力的传播特性,建立了基于WALE湍流模型及Zimont预混火焰模型的油气爆炸模型;模拟了6种不同分支管道结构空间内汽油/空气混合物爆炸发生发展过程;研究了分支管道数量及相对设置位置对爆炸超压的影响规律,以及分支管道对火焰传播形态和速度的影响规律;模拟结果与前人相关实验规律进行对比.研究结果表明:分支管道对汽油/空气混合气预混爆炸具有明显的强化激励作用;火焰锋面传播经过分支管道时,经历规则—褶皱—规则的变化过程;主管道内火焰传播速度,在分支管道对流场的突扩作用和湍流作用的共同影响下呈震荡变化的规律.【期刊名称】《中国安全生产科学技术》【年(卷),期】2019(015)001【总页数】5页(P134-138)【关键词】分支管道;油气;数值模拟;超压变化;火焰特性【作者】LIU Chong;DU Yang;ZHANG Peili;MENG Hong;LI Shu;SUN Xiaokang【作者单位】【正文语种】中文【中图分类】X9320 引言当分支结构内发生可燃气爆炸时，受空间特征影响，爆炸湍流扰动会大幅增强，爆燃火焰迅速发展，甚至发生爆轰，从而导致严重事故后果。
因此，较多研究者对包含分支结构的管道可燃气爆炸开展了大量的实验和数值模拟研究[1-3]。
杨志等[4]研究了丙烷/氧气/空气预混可燃气爆燃火焰、稳定爆轰波及非稳定爆轰波通过“Z”型管道时的传播规律；Xiao等[5]研究了丙烷/空气预混可燃气在含有90°弯头管道中发生爆炸火焰传播特征；张家山等[6]利用3种角度的分岔管道研究了分支结构对甲烷爆炸传播的影响。
在单质可燃气体研究的基础上，油气这个混合工质的预混爆炸传播特征受分支结构影响规律的研究日益受到重视。
International Conference on Manufacturing Engineering and Intelligent Materials (ICMEIM 2017)A Numerical Analysis on the Capability of Withstanding Violent Typhoonof Distribution FeedersHui-hua Deng1,Chun-yan Huang2,*,Shao-hui Huang3,Jian-hua Chen1andFeng-liu Liang11.Huizhou Power Supply Bureau, Guangdong Power Grid Co., Ltd, Huizhou 516001, China;2. Guangzhou Power Electric Technology Co., Ltd, Guangzhou 510640, China;3. Huizhou Electric Power Design Institute, Huizhou 516001, ChinaKeywords: Distribution Feeder, Violent Typhoon, Wind Capability.Abstract: Distribution feeders are sometimes damaged heavily by typhoon every year in the coastal region. A finite element model of a standard feeder is established by ABAQUS/CAE firstly. Then the deformation under different wind speeds after the wind loading is applied by equivalent inertial acceleration. The paper focus on investigating the deflection of the pole of three kinds of feeders, which cover the effect of foundation soil, strengthened with guy wire and none of both. IntroductionAs a place appearing typhoon frequently, the coastal area of China suffers to typhoon every year. The grid feeders, especially the overhead distribution lines are destroyed most heavily [1], because of its low wind standing design grade, circuit aging and maintenance shortage. The studies about power grid disaster resistance are mainly focus on the electric transmission feeders [2], few on the theoretical research of distribution lines. The grid companies have put huge resource into the reinforcement and reconstruction on the distribution feeders [3]. Since there are no exact theoretical analysis and numerical simulation, the reinforcing works depend on experience and gained less effect.Finite element modeling is a numerical analysis method. It can be used to investigate the mechanics response of a whole system under all kinds of loading and has been applied in the static and dynamic analysis of transmission feeders. Liu established the finite element models of 220kV and 550kV overhead transmission lines to simulate the dynamic windage response [4]. The model neglected the pole’s deformation. Aimed at 550kV two-circuit transmission lines, Yan built a tower-line coupling finite element model to study the dynamic response of the system under different ice unloading condition [5]. Lou researched the dynamic windage response of 500kV strain section with eight spans by FEM and harmonic superposition method [6]. Shao discussed the vibration and oscillation of the wire caused by wind [7].The detail investigation on the anti-wind capability, the inner force and deflection of the RC pole haven’t been reported. This paper presents a numerical analysis on the capability of withstanding violent typhoon of 10kV distribution feeders. A finite element model of a standard strain section is established by ABAQUS [8]. Then the deflection of the pole under different wind speed and three kinds of conditions are discussed.Model BuildingFinite Element ModelBase on a standard single circuit overhead line, a pole-wire coupling finite element model is built by ABAQUS/CAE. In the model, the pole, high tensile steel wire, pole arm and wire are divided into 5760 solid elements (C3D8R), 382 truss elements (T3D2), 200 beam elements (B32) and 1202 truss elements (T3D2), respectively. The constraint relationship between the insulator and the wire is coupling, and that between insulator and pole arm is fixation.Loading SimulationThe loading of a distribution line includes the gravities of wire, pole arm and RC pole, and the wind loading that the wire and pole subjected. The gravity should be applied to the model by gravitational acceleration, and the wind loading can be applied after be translated to equivalent gravitational acceleration.Size and ParametersThe RC pole discussed in this paper is a M Grade high strength pole, whose size is: height 12m, base diameter 350mm, top diameter 190mm, wall thickness 60mm, burial depth 2m. The concrete grade is C60. In the concrete, arranges 19 9 high-tensile wire, with standard value of strength 1470MPa, tensile strength 1040MPa, compressive strength 410MPa, and elasticity modulus 205GPa. The wire’s type is JL/GIA-150/20, diameter 16.67mm, cross sectional area 164.5mm2, equivalent density 3339.8kg/m3, integrated elastic coefficient 73GPa, intensity strength of conversion 283.5MPa. The span of the circuit is 60m. The cross arm uses Steel Q345, type ∠75×6. Diagonal bracing uses Steel Q235, type∠50×5, elasticity modulus 201GPa. The guy wire is steel strain GJ50, which is advised by South China Grid’s Typical Design Guide.Calculation ResultsIn the following study, the pole’s deflection under different wind speed and three kinds of conditions are discussed. After just a little modification needed to be made to the model built in Section 1, a new model suited to the investigation can be obtained.Model 1Model 1 is the simply model shown in Fig.1, which neglect the foundation soil and wind guy wire. The restrain condition at the section of ground is defined as fixed. Fig.1 shows the deflection of the pole under different wind speeds, which change from 25m/s to 50m/s.It can be known from Fig.1(a) that the deflection of the pole’s top linearly increase with wind speed. Fig.1(b) shows that when wind speed equal or greater than 35m/s, i.e., the typhoon level, the deformation enlarges rapidly.(a) Deflection of the pole’s top (b) Pole deflection curveFigure 1. Deflection of Model 1Model 2In Model 2, we consider the influence of the foundation soil in a 1m radius around the root of the pole. The constitutive relation employs Mohr-Coulomb model. Assuming the soil common clay, the soil is divided into 1440 solid elements (C3D8R). The specific parameters are given in Table 1.Table 1. The soil parameters SoilpropertyModulus of compression E S /[MPa]Poisson’s ratio μ DesityΡ/[kg·m -3] Cohesion C /[KPa] Internal friction angle Β/[°] Dilatancy angle φ/[°] Clay 18 0.3 1880 107 35 17.5The calculation results of the pole’s deformation are shown in Fig.2. It can be concluded from Fig.2(a) that under the same wind speed the top deflection of Model 2 are greater than that of Model1. The increment are about 6~13cm ，since the deformation of the soil have superimposed effect on the pole. Comparing with Fig.1(b), the pole deflections in Fig. 2(b) are greater, and the zero point lies in 1.2m below the ground. If the common clay is replaced with soft plastic clay, the aggravate soil compression will leads the pole deformation to further increasing. So, the worse foundation soil means the greater chance for pole toppled than broken.(a) Deflection of the end (b) Pole deflection curveFigure 2. Deflection of Model 2Model 3Model 3 is strengthened by guy wire. The guy wire, 30 angle to the pole, made of GJ50 steel strand, is installed at the hoop of the diagonal bracing of the cross arm. The calculation results are shown in Fig.3. It can be known from Fig.3(a) that the top deflections increase a little when the wind speed rise. Comparing to the curves in Model 1 and Model 2, the deflection of Model 3 is kept in a low level. Fig.3(b) indicates that the pole deflection curve has a turn at the section where the guy wire installed. Even at the violent typhoon speed of 50m/s, the maximum displacement is only 0.022m. The obvious and great reinforcement effect is verified.(a) Deflection of the end (b) Pole deflection curveFigure 3. Deflection of Model 3ConclusionsThe paper made a numerical study on the capability of withstanding violent typhoon of 10kV distribution feeders. A coupling finite element model of a standard stain section is established by ABAQUS. The deflections of the pole under three kinds of condition and different wind speed are investigated. The results indicate that: (1) the deformation of the foundation soil has superimposed effect on the pole deflection. If the soil property is poor, the pole tends to topple. (2) installing guy wire can decrease the maximum displacement of the pole obviously and increase the capability of anti-wind of the feeder. The research results can provide reference to the reinforcement design of distribution feeders.References[1] Feng Wang, Lijuan Li, Canbing Li, et al. 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Conductor swinging dynamic characteristic and calculation model of continuous multi-span transmission line [J]. Electric Power Construction, 2015, 36(2): 1-8.[7] Shao Tianxiao. Mechanical calculation on transmission line [M]. Beijing: China Electronic Power Press, 2003.[8] CAX Technique Alliance, Chen Haiyan. ABAQUS Finite Element Analysis, From Beginner to Master (2nd ed.) [M]. Beijing: Electronic Industry Press, 2015.。
