The propagation law and analysis of gas explosion in U type duct

In order to explore the propagation law of gas explosion in U type laneways,the propagation law of flame and shock wave in U type duct were experimentally and theoret- ically investigated.It is shown that the shock wave takes on the complicated stress state and the flame takes on complicated change rules in the U type duct.The propagation process of gas explosion in bend duct is the mutual action of explosion wave,flame and complicate flow,the destruction in bend surface is especially serious.In the mine exploita- tion and laneway design,the bend laneway should be avoided,especially continuous bend laneway.

Modeling stochastic mortality with O-U type processes

Modeling log-mortality rates on O-U type processes and forecasting life expectancies are explored using U.S. data. In the classic Lee-Carter model of mortality, the time trend and the age-specific pattern of mortality over age group are linear, this is not the feature of mortality model. To avoid this disadvantage, O-U type processes will be used to model the log-mortality in this paper. In fact, this model is an AR(1) process, but with a nonlinear time drift term.Based on the mortality data of America from Human Mortality database(HMD), mortality projection consistently indicates a preference for mortality with O-U type processes over those with the classical Lee-Carter model. By means of this model, the low bounds of mortality rates at every age are given. Therefore, lengthening of maximum life expectancies span is estimated in this paper.

复杂岩体中锆石的成因判识及其对锆石U-Pb年龄的影响:以辽河坳陷太古宇基底中的锆石为例

复杂岩体经历了长期地质演化,内部所含锆石成因十分复杂。综合前人研究成果,根据锆石外部形态、CL发光强度、内部结构以及微量元素特征,本文将锆石成因类型归纳为岩浆作用、变质作用以及热液作用3大类9小类。在锆石U-Pb定年的过程中,单颗粒锆石或锆石上不同位置的成因判识是获取高质量U-Pb年龄数据的前提。以渤海湾辽河坳陷基底复杂岩体为例,对岩体内具有核—边结构的复杂成因锆石进行了系统的研究,分别获取不同成因锆石的U-Pb年龄,进而探讨锆石成因对获取高质量U-Pb年龄的重要意义。阴极发光图像显示,锆石的核部多见岩浆成因环带结构,也可见斑杂状、海绵状及扇形分带等变质成因结构,边部呈现变质重结晶成因的扇形和冷杉叶结构。锆石核部Th/U比值(0.39~1.32)和分散的稀土元素特征,表明核部存在岩浆结晶锆石、变质锆石以及变质残余锆石,边部主要是变质重结晶作用或流体蚀变形成的增生边。基于锆石的成因类型划分,从3个样品锆石核部和边部分别获得了代表原岩形成时间的岩浆年龄和变质作用时间的变质年龄。辽河坳陷基底复杂岩体锆石U-Pb年龄结果表明,基底存在两期新太古代晚期岩浆事件,分别为2586~2583 Ma、2565~2538 Ma,变质事件主要发生在2508~2501 Ma。辽河坳陷基底岩浆事件和变质事件的获得,对于揭示华北克拉通覆盖区前寒武纪基底的形成演化具有重要意义。

皖南伏岭A型花岗岩的成因——地球化学、锆石U-Pb年龄及Lu—Hf同位素特征

伏岭花岗岩体,位于江南造山带东段的皖浙相邻区,岩浆岩沿着近北东向的宁国—绩溪深大断裂断分布。笔者等对伏岭岩体鱼龙川(γ_(5)^(3-2))单元花岗岩开展了系统的全岩岩石地球化学、LA-ICPMS锆石U-Pb同位素年龄和锆石原位Lu—Hf同位素地球化学研究,结果表明,花岗岩的侵位年龄为131.8±0.9 Ma,富硅、富碱、贫钙、贫铁,具有较高的Rb、Th、U、Ga、Zr和Y含量,较低的Sr、Ba和Nb含量,稀土配分曲线呈现典型的“海鸥式”分布特征,显示强烈的负Eu异常;微量元素原始地幔标准化蛛网图显示明显的Ba、Sr、Nb的负异常。其高SiO_(2)含量和Rb/Sr值、低Ba、Sr含量具备江南造山带东段皖南地区A型花岗岩的典型特征。岩体具有同源岩浆演化特征,源区可能存在磷灰石、钛铁矿的分离结晶作用,而辉石类的分离较少。伏岭岩体主要来源于地壳中镁铁质岩石的部分熔融,其地球化学特征继承于源岩。锆石ε_(Hf)(t)变化范围较小,均在-7.0~-4.6之间,二阶段模式年龄(TDM2)为1478~1630 Ma,伏岭花岗岩可能由中元古代古老下地壳部分熔融形成。伏岭岩体的形成可能受到碰撞作用的影响,岩体形成于后碰撞期,中元古代的基底岩石被大范围的熔融,从而产生了伏岭A型花岗岩。

Improvement of breakdown characteristics of an A1GaN/GaN HEMT with a U-type gate foot for millimeter-wave power application

In this study, the physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of an AlGaN/GaN high electron mobility transistor （HEMT） with a U-type gate foot. The U-gate AlGaN/GaN HEMT mainly features a gradually changed sidewall angle, which effectively mitigates the electric field in the channel, thus obtaining enhanced off-state breakdown characteristics. At the same time, only a small additional gate capacitance and decreased gate resistance ensure excellent RF characteristics for the U-gate device. U-gate AlGaN/GaN HEMTs are feasible through adjusting the etching conditions of an inductively coupled plasma system, without introducing any extra process steps. The simulation results are confirmed by experimental measurements. These features indicate that U-gate A1GaN/GaN HEMTs might be promising candidates for use in millimeter-wave power applications.

U型Twin-PBL剪力键极限承载力的数值分析

根据端部承压混凝土可提高Twin-PBL剪力键承载能力的特点,提出一种新型的可用于装配式钢混组合结构的间断式U型Twin-PBL剪力键。通过3组推出试验试件的非线性数值模拟分析,研究了这种新型剪力键的极限承载特点和承载力。结果表明:U型Twin-PBL剪力键极限承载能力较普通承压型Twin-PBL剪力键有显著提高,且提高主要来源于端部混凝土承压面积增大,所以混凝土强度的提高对该剪力键承载能力影响明显,而孔中混凝土榫和贯穿钢筋两部分对承载力贡献无明显变化,故而通过修正端承压混凝土面积得到了这种剪力键承载力计算公式。研究结果为装配式钢-混凝土组合梁桥的间断式剪力键提供了新的思路。

Petrogenesis of Late Cretaceous Jiangla＇angzong I-Type Granite in Central Lhasa Terrane, Tibet, China： Constraints from Whole-Rock Geochemistry, Zircon U-Pb Geochronology, and Sr-Nd-Pb-Hf Isotopes

The Jiangla＇angzong granite in the northern part of the Central Lhasa Terrane is composed of syenogranite and adamellite. LA-ICP-MS zircon U-Pb analyses suggest that syenogranite has a weighted mean 2±6pb/23SU age of 86±1 Ma （mean square weighted deviation=0.37）, which is in accordance with the muscovite Ar-Ar age （85±1 Ma） of Cu-Au ore-bearing skarns and the zircon U-Pb age （84±1 Ma） of adamellite. This suggests that the Jiangla＇angzong magmatism and Cu-Au mineralization events took place during the Late Cretaceous. The granite contains hornblende, biotite, and pyroxene, and does not contain Al-bearing minerals, such as muscovite, cordierite, and garnet. It has high contents of SiO2 （65.10 -70.91wt%）, K20 （3.44-5.17wt%）, and total K20＋Na20 （7.13-8.15wt%）, and moderate contents of A12Oa （14.14-16.45wt%） and CaO （2.33-4.11wt%）, with a Reitman index （δ43） of 2.18 to 2.33, and A/ CNK values of 0.88 to 1.02. The P205 contents show a negative correlation with SiO2, whereas Pb contents show a positive correlation with SiO2. Th and Y contents are relatively low and show a negative correlation with the Rb contents. These characteristics suggest that the Jiangla＇angzong granite is a high K calc-alkaline metaluminous I-type granite. It is enriched in light rare earth elements （LREE） and large ion lithofile elements （LILE）, and depleted in heavy rare earth elements （HREE） and high field strength elements （HFSE）, with LREE/HREE ratios of 11.7 to 18.1. The granite has negative Eu anomalies of 0.58 to 0.94 without obvious Ce anomalies （δCe=l.00-1.04）. The relatively low initial a7Sr/a6Sr ratios of 0.7106 to 0.7179, positive ε±nt（t） values of 1.0 to 4.1, and two-stage Hf model ages （TDM2） ranging from 889 Ma to 1082 Ma, These geochemical features indicate that the granite derived from a juvenile crust. The （143Nd/144Nd）t values from the Jiangla＇angzong granite range from 0.5121 to 0.5123, its eNd（t） values range from -10.17 to -6.10, its （^206pb /^204pb）t values range from 18.683 to 18.746, its （^207pb /^204pb）t values range from 15.695 to 15.700, and its （^208pb /^204pb）t values range from 39.012 to 39.071. These data indicate that the granite was formed by melting of the upper crust with the addition of some mantle materials. We propose that the Jiangla＇angzong granite was formed during the post- collision extension of the Qiangtang and Lhasa terranes.

U型平板微热管LED散热器散热性能分析

针对目前LED表面发热量较大,局部温度过高,而导致其使用寿命减少的问题,该研究以平板微热管为核心传热元件,与锯齿形翅片结合,设计了一种U型平板微热管散热器。采用试验和仿真模拟相结合的方法,对不同风速、翅片结构、翅高及翅间距等关键影响因素进行分析。结果表明:通过对比分析U型平板微热管在两种室外工况下各测点试验值和模拟值,散热稳定后温度的最大误差分别为4.2%和6.7%,验证了模型的可靠性。风速分别为0.5和3.0 m/s时,锯齿型翅片都具有良好的散热性能。当风速为3.0 m/s时,锯齿型翅片、W型翅片、直翅片散热器稳定后热源温度分别为34.3、35.5和39.1℃。为找到最佳工况和结构,进行了正交分析,当室外风速为3.5 m/s,锯齿型翅片翅高为12 mm,翅间距为8 mm时,U型热管具有较佳的散热性能。研究结果可为LED散热系统的设计提供数据参考和设计思路,拓宽LED光源的应用范围。

U-Type Designs via New Generalized Partially Balanced Incomplete Block Designs with <i>m</i>= 4, 5 and 7 Associated Classes

The traditional combinatorial designs can be used as basic designs for constructing designs of computer experiments which have been used successfully till now in various domains such as engineering, pharmaceutical industry, etc. In this paper, a new series of generalized partially balanced incomplete blocks PBIB designs with m associated classes (m = 4, 5 and 7) based on new generalized association schemes with number of treatments v arranged in w arrays of n rows and l columns (w ≥ 2, n ≥ 2, l ≥ 2) is defined. Some construction methods of these new PBIB are given and their parameters are specified using the Combinatory Method (s). For n or l even and s divisor of n or l, the obtained PBIB designs are resolvable PBIB designs. So the Fang RBIBD method is applied to obtain a series of particular U-type designs U (wnl;) (r is the repetition number of each treatment in our resolvable PBIB design).

基于陶瓷基微热板阵列的U盘式气体检测仪

针对目前基于MEMS传感器阵列的气体检测仪所存在的弊端,开发了一种基于陶瓷基微热板阵列的U盘式气体检测仪。此检测仪以16元微热板气体传感器阵列芯片为器件,通过微控制器实现信号采集、温度控制、无线传输等功能。它还可以通过USB、WiFi或蓝牙实现无线通信。该检测仪尺寸小,功耗低,对多种气体有着良好的响应,可广泛应用于多种实际场所。

基于新材料应用的轻量化U型自卸车厢的优化仿真

自卸车是重型商用车最基础的一款专用车产品。在我国近几年的自卸车行业发展中,随着国家对环境的重视,在生产制作和使用中矩形箱结构重量大的问题日益突出,车厢结构开始由原来的矩形箱逐渐开始向U型车厢转变。文章模型采用三维软件SolidWorks造型建模,采用高效的有限元软件进行分析。模拟不同路况及装载情况下的车厢受力情况,根据分析结果从钢板材质和车厢结构方面对车厢进行优化。

New Evidence for Genesis of the Zoige Carbonate-Siliceous-Pelitic Rock Type Uranium Deposit in Southern Qinling:Discovery and Significance of the 64 Ma Intrusions

The carbonaceous-siliceous-argillitic rock type uranium deposit in the Zoige area is located in the northeastern margin of the Tibetan Plateau, and has gained much attention of many geologists and ore deposit experts due to its scale, high grade and abundant associated ores. Because of the insufficient reliable dating of intrusive rocks, the relationship between mineralization and the magmatic activities is still unknown. In order to study this key scientific issue and the ore-forming processes of the Zoige uranium ore field, the LA-ICP-MS zircon U-Pb dating of magmatic rocks was obtained：64.08±0.59 Ma for the granite-prophyry and ~200 Ma for the dolerite. U-Pb dating results of uraninite from the Zoige uranium ore field are mainly concentrated on ~90 Ma and ~60 Ma. According to LA-ICP-MS U-Pb zircon dating, the ages for the dolerite, porphyry granite and granodiorite are 200 Ma, 64.08 Ma approximately and 226.5-200.88 Ma, respectively. This indicates that the mineralization has close relationship with activities of the intermediate-acidic magma. The ages of the granite porphyry are consistent with those uraninite U-Pb dating results achieved by previous studies, which reflects the magmatic and ore-forming event during the later Yanshanian. Based on the data from previous researches, the ore bodies in the Zoige uranium ore field can be divided into two categories：the single uranium type and the uranium with polymetal mineralization type. The former formed at late Cretaceous（about 90 Ma）, while the latter, closely related to the granite porphyry, formed at early Paleogene（about 60 Ma）. And apart from ore forming elemental uranium, the latter is often associated with polymetallic elements, such as molybdenum, nickel, zinc, etc.

Petrogenesis and Mineralization of Two-Stage A-Type Granites in Jiuyishan,South China:Constraints from Whole-rock Geochemistry, Mineral Composition and Zircon U-Pb-Hf Isotopes

The Jiuyishan complex massif,located in the northern section of the Nanling region,is a combination of five plutons,namely,the Xuehuading,Jinjiling,Pangxiemu,Shaziling and Xishan plutons.Whole-rock geochemistry,Imineral electron microprobe analysis,zircon U-Pb dating and Hf isotope analysis were carried out for the Jinjiling and Pangxiemu plutons.The zircon U-Pb dating yields weighted mean ages of 152.9±0.9 Ma for the Jinjiling pluton and 151.7±1.5 Ma for the Pangxiemu pluton,with a narrow gap between them.The Jinjiling and Pangxiemu plutons both have geochemical characteristics of high SiO2,Al2 O3,Na2 O,K2 O and low TiO2,MgO,CaO,P2 O5 contents,with intense depletions in Sr,Ba,Ti,Eu and enrichments in Ga,FeoOT and HFSE,and these characteristics reflect an A-type affinity.From the Jinjiling to the Pangxiemu plutons,the mineral composition of mica changes from lepidomelane to zinnwaldite,with increases in F,Li2 O and Rb2 O contents.The mineral composition of zircon changes from low Zr/Hf to high Zr/Hf,with increasing HfO2,P2 O5 and UO2+ThO2+Y2 O3 contents.The mineral compositions of feldspar indicate that the Pangxiemu pluton contains more alkali feldspar than the Jinjiling pluton.The whole-rock geochemistry and mineral compositions reveal a higher degree of differentiation for the Pangxiemu pluton.The nearly uniformεHf(t)indicates the same source region for the two plutons:both were derived from partial melting of the lower crust,with small contributions of mantle materials.In addition,higher F,lower Nb/Ta and Zr/Hf ratios in the Pangxiemu Pluton suggest a closer relationship with the rare metal mineralization than for the Jinjiling pluton.

基于磁导率无损检测的双U型探头仿真优化研究

基于磁导率无损检测原理,设计了一种双U型检测探头。以20钢试件为研究对象,通过模拟仿真分析了双U型探头在检测过程中的关键影响参数与检测灵敏度的关系,对关键影响参数进行了优化选取,又通过试验研究了拉应力对检测灵敏度的影响。结果表明,检测灵敏度随着激励电压幅值的升高而增大,随着激励频率的提高先增大后趋于稳定,随着激励线圈匝数的增加而下降,随着拉应力的增大而减小,双U型探头相比于传统U型探头具有更广泛的分析检测能力。该仿真研究为后续探头的选取制作提供了设计理念和理论依据。

U形板焊接机器人设计与运动仿真

针对船舱狭小空间U形板角焊缝焊接工况,设计了一款类轨道悬挂式移动焊接机器人。该焊接机器人由移动机器人本体、两自由度机械臂及焊炬组成,三自由度实现焊接位置调节。首先,介绍了焊接机器人的结构设计;其次,分析了U形板最小转弯半径与机器人各变量之间的参数关系,确保转弯要求;最后,利用ADAMS仿真机器人移动过程,研究多个变量对焊炬末端在Y、Z方向偏移及振动的影响。结果表明:移动过程中,焊炬在机器人中间时的焊接轨迹最易控制;夹紧轮Z向位置为24.25mm,移动过程中Z方向偏移稳定,Y、Z方向振动微小;满足结构安装前提下,应选择刚度较大的弹簧;弹簧预紧力为20N时,Y、Z方向偏移、振动均得到较大改善。

倒U型自支撑管系稳定性分析

为探究倒U型自支撑管系在施工和运行条件下的稳定性能,采用非线性有限元计算方法研究施工偏差、施工外力、水压试验和管系内压因素对其稳定性的影响。计算结果表明:施工偏差、施工外力、水压试验都会降低倒U型自支撑管系稳定性能,管系内压对其稳定性能有利。倒U型自支撑管系对施工的初始倾斜偏差较为敏感,缺陷值为1/1000时,稳定安全系数仅降低0.8%,而当缺陷值达到4/135时,稳定安全系数降低了24.6%。施工水平外力和垂直外力的极限荷载计算荷载分别为339 N和1339 N,在施工过程中须格外注意。水压试验使其稳定性明显降低,将导致管系存在稳定安全风险,故而须给予管系足够的外部支撑,保证其平面外稳定。

U形沟一次成型模板施工技术研究与应用

模板工艺是影响现浇混凝土成型效果的重要因素。针对工程中U形沟二次浇筑成型施工缝衔接质量差、工效低、进度慢等问题,经深入研究分析,优化改进为一次成型装配式组合模板施工技术,取得了浇筑成型质量高、建设工期短、建造成本低的效果。通过工程实例,系统全面地介绍了U形沟一次成型模板施工技术,可为类似工程提供参考。

基于有限元法的U型钢卡缆受力分析研究

随着煤矿开采深度增大,支护难度也成倍提升。U型钢可缩性支架被广泛地应用于深部矿山巷道支护。卡缆是U型钢可缩性支架的关键部件,其性能直接影响着U型钢支架的支护承载性能。在理论分析U型钢拱形支架在不同受载情况下的变形特点的基础上,借助ABAQUS有限元数值计算软件,分别研究了双槽夹板卡缆在圆弧形和椭圆弧形2种型钢搭接段滑移时的力学特性,并且分析了U型钢螺栓的受力特征,得到了双槽夹板卡缆对U型钢拱形支架的约束作用会受到搭接段曲率不匹配度的影响的结论,提出了控制U型钢失效的建议。对于确保地下工程U型钢支架的稳定支护具有重要意义。

煤矿U型带式输送机转弯段应力影响因素分析

以LJY5型带式输送机为研究对象,介绍一种基于有限元分析的煤矿U型带式输送机转弯段应力影响因素分析方法。该方法先将输送机转弯段相关参数输入到SolidWorks软件内,构建出相应的转弯段皮带模型,然后将模型导入至Ansys软件,以此对模型划分网格,并在设定约束条件与载荷条件下,从托辊间距、拉力、转弯半径等方面出发,分析U型带式输送机转弯段应力影响因素,以此为U型带式输送机转弯段的优化设计提供支持,确认该方法具有一定应用价值。

短视频个性化推荐与使用意愿的倒U形关系研究

[目的/意义]个性化推荐在促进信息系统使用方面具有积极作用,但过度的个性化推荐也会造成用户的隐私忧虑以致降低使用意愿。短视频情境下,个性化推荐与使用意愿之间的具体关系目前还不清楚。[方法/过程]基于隐私计算理论,探索短视频个性化推荐与用户使用意愿之间的非线性关系。划分短视频类型并选取实用型短视频、享乐型短视频和隐私关注作为调节变量。运用层次回归分析的方法,应用Stata软件对假设进行验证。[结果/结论]个性化推荐与短视频使用意愿之间存在倒U形关系;隐私关注对倒U形关系存在显著的调节作用;不同类型短视频对倒U形关系的影响存在差异,且仅有实用型短视频的调节作用得到验证。