Theoretical and Experimental Investigation of Flexural Vibration Transfer Properties of High-Pressure Periodic Pipe

According to the theory of phononic crystals, the hydraulic pipeline is designed to be a periodic structure composed of steel pipes and hoses to suppress the vibration of the hydraulic system with band gaps. We present theoretical and experimental investigations into the flexural vibration transfer properties of a high-pressure periodic pipe with the force on the inner pipe wall by oii pressure taken into consideration. The results show that the vibration attenuation of periodic pipe decreases along with the elevation of working pressure for the hydraulic system, and the band gaps in low frequency ranges move towards high frequency ranges. The periodic pipe has good vibration attenuation performance in the frequency range below 1000 Hz and the vibration of the hydraulic system is effectively suppressed. A11 the results are validated by experiment. The experimental results show a good agreement with the numerical calculations, thus the flexural vibration transfer properties of the high- pressure periodic pipe can be precisely calculated by taking the fluid structure interaction between the pipe and oil into consideration. This study provides an effective way for the vibration control of the hydraulic system.

Numerical Study of Turbulent Periodic Flow and Heat Transfer in a Square Channel with Different Ribs

A numerical investigation has been carried out to examine turbulent flow and heat transfer characteristics in a three-dimensional ribbed square channels. Fluent 6.3 CFD code has been used. The governing equations are discretized by the second order upwind differencing scheme, decoupling with the SIMPLE (semi-implicit method for pressure linked equations) algorithm and are solved using a finite volume approach. The fluid flow and heat transfer characteristics are presented for the Reynolds numbers based on the channel hydraulic diameter ranging from 104 to 4 ′ 104. The effects of rib shape and orientation on heat transfer and pressure drop in the channel are investigated for six different rib configurations. Rib arrays of 45° inclined and 45° V-shaped are mounted in inline and staggered arrangements on the lower and upper walls of the channel. In addition, the performance of these ribs is also compared with the 90° transverse ribs.

Second-order two-scale computations for conductive radiative heat transfer problem in periodic porous materials

In this paper, a kind of second-order two-scale （SOTS） computation is developed for conductive-radiative heat trans- fer problem in periodic porous materials. First of all, by the asymptotic expansion of the temperature field, the cell problem, homogenization problem, and second-order correctors are obtained successively. Then, the corresponding finite element al- gorithms are proposed. Finally, some numerical results are presented and compared with theoretical results. The numerical results of the proposed algorithm conform with those of the FE algorithm well, demonstrating the accuracy of the present method and its potential applications in thermal engineering of porous materials.

大高宽比矩形腔体侧向正弦加热下对流扰动的成长和传热特性

为了研究矩形腔体侧向正弦周期加热条件下对流扰动的成长和传热特性,本研究对流体力学方程组进行了数值模拟。结果表明:随着格拉晓夫数Gr的增加,对流扰动的最大振幅Amax的成长率变大,线性成长阶段的时间变短。对于高宽比A=10,腔体宽度d=2cm的腔体,普朗特数Pr=6.949的流体,对流扰动的成长率γ_(m)随着格拉晓夫数Gr变化的经验式为γ_(m)=9×10^(-8)Gr^(1.2343);对于高宽比A=10、腔体宽度d=6cm的腔体,普朗特数Pr=0.703的流体,成长率m随着格拉晓夫数Gr的变化关系式为m=8×10^(-4)Cr^(0.52)。当Pr=0.0272时,热壁面平均努塞尔数Nu和格拉晓夫数Gr的关联式为Nu=0.00002Gr^(1.17);当Pr=6.949时,Nu=0.00024Gr^(1.05)。随着格拉晓夫数Gr数增加,右壁面的传热能力增强。

基于PSS+PXF的ISF高精度振荡器噪声分析模型

提出了一种基于PSS+PXF的ISF的相位噪声模型,用于预测振荡器的相位噪声。该模型相对传统的拉扎维模型考虑了振荡器的非线性时变特性,因此更加精确。通过仿真验证了该模型的有效性,基于PSS+PXF的ISF的相位噪声模型精度相比传统拉扎维模型提升200%以上。

高阶声学相对传递函数的参数化辨识

针对声学相对传递函数的模型阶次高以及辨识数据信噪比低的问题,文章运用频域系统辨识方法,建立了一种相对传递函数的高精度参数化辨识方法。首先建立变量带误差辨识框架,采用周期扫频信号作为声源激励,给出声学相对传递函数的极大似然算法。然后使用正交福赛斯(Forsythe)多项式解决高阶系统带来的雅克比矩阵条件数过高的数值问题,并建立了极大似然方法所需初始值的生成策略。最后通过仿真算例和实验测试,验证文中方法在混响声场下辨识声学相对传递函数的有效性。

考虑可变接续时间窗的高铁周期列车运行图优化

精准高效的换乘接续设计对于周期列车运行图在我国的全面推广至关重要。我国高速铁路网络结构复杂、空间跨度广,不同距离的换乘客流OD所能接受的中转换乘时间范围有着明显的不同。现有研究对换乘接续时间的考虑多基于固定接续时间窗,造成实际换乘时间与各OD旅客可接受的换乘时间不匹配,限制了换乘服务水平的进一步提升。基于此,结合“事件-活动”网络和周期事件规划问题(Periodic Event Scheduling Problem,PESP),构建了考虑可变接续时间窗的高铁周期列车运行图优化模型,实现了列车接续关系选择、OD换乘接续关系分配、换乘时间优化的同步决策。模型首先引入OD换乘接续关系分配变量,使得模型可在优化过程中动态决策列车接续关系是否为特定客流OD提供服务。在此基础上,引入了可变接续时间窗约束,实现列车接续时间窗根据所分配客流OD合理换乘时间范围动态确定。同时,设计了最小化周期列车运行图换乘服务水平与理想服务水平偏差的线性化目标函数,使得模型得以在GUROBI整数规划求解器中求解。研究案例编制了京沪高铁以及与之衔接的部分高铁线路路网周期列车运行图,与固定换乘接续时间窗的研究案例相比,换乘服务频率和换乘接续时间指标均有显著提升,验证了所提模型的正确性及有效性。

新型简易移送垫在手术室围手术期过床转运的应用效果

目的探讨新型简易移送垫在手术室围手术期过床转运的应用效果。方法选取2022年8月至2023年2月南昌市第一医院100例手术患者为研究对象,按随机数字表法分为对照组(50例)和观察组(50例)。对照组使用传统搬运方法,观察组使用新型简易转运移送垫搬运,比较两组的不良事件发生率、患者舒适满意度、过床搬运时间及医护人员腰肌损伤发生率。结果观察组的不良事件总发生率低于对照组,差异有统计学意义(P<0.05);观察组患者舒适度高于对照组,差异有统计学意义(P<0.05);观察组过床搬运时间短于对照组,差异有统计学意义(P<0.05);观察组医护人员腰肌损伤总发生率低于对照组,差异有统计学意义(P<0.05)。结论通过新型简易转运移送垫在术后手术室与临床科室过床搬运的应用,从而避免搬运过程中坠落、管道脱落或牵扯等不良事件发生,给患者增加舒适及安全感,提高患者舒适满意度,降低临床医护人员搬运时导致的腰肌劳损的发生率,值得临床推广。

三维点阵结构拓扑开发研究进展及其对流传热性能对比

系统综述了国内外三维点阵结构拓扑开发的研究现状,分别在等流量、等压降和等泵功条件下对比了其总体传热与散热性能.在模型验证的基础上,针对12种具有相同特征尺寸和孔隙率的点阵结构,分别在6种不同点阵材质、两种不同取向下开展了数值模拟与性能对比.结果表明:点阵拓扑、点阵材质及运行工况对其传热和散热性能优劣具有显著影响;不同条件下,性能最优的点阵不尽相同.在等流量下,A向节点偏移X点阵和A向八叉树点阵的传热性能最优,A向节点偏移X点阵的散热性能最优.在等压降下,A向节点偏移X点阵和B向节点偏移X点阵的传热性能最优,B向立方点阵和B向节点偏移X点阵的散热性能最优.在等泵功下,A向节点偏移X点阵和B向矩形杆金字塔点阵的传热性能最优,B向节点偏移X点阵和B向矩形杆金字塔点阵的散热性能最优.在固定孔隙率和特征尺寸下构建了现有点阵结构的传热与散热性能数据库,可作为新型点阵拓扑开发的比较基准,同时,可为不同工程设计中点阵结构的选型提供指导.

脑卒中患者医院-家庭过渡期护理的研究进展

对过渡期护理的概念、脑卒中患者医院-家庭过渡期护理发展现状、我国脑卒中患者过渡期护理存在问题及顺利过渡的改善策略等进行综述,旨在为构建适合我国脑卒中患者的过渡期护理模式、护理方案提供依据,为更好地维护并促进脑卒中患者的康复和健康提供借鉴。

论出资未届期股权转让出让人的补充责任——新《公司法》第八十八条第一款的解释论

出资未届期股权转让后出让人是否担责在我国司法裁判中分歧明显,存在出让方不担责和出让方担责两种观点。根据《中华人民共和国公司法》第八十八条第一款的规定,未届期股权转让后由出让人在受让人未按期足额缴纳出资时承担补充责任。出让人承担补充责任的法理依据有四:股东有限责任之约束、资本充实原则的要求、出资义务的法定性及特殊情形下发起人作为控股股东转让股权负有信义义务。该补充责任具有法定性、补充性、有限性、无过错、一次性特征,其适用应当具备严格的要件。主体要件方面,可以诉请转让人承担补充责任的原告为公司及其执行机关和公司债权人两类;被告为股权出让人,具体需要根据股权一手转让抑或多手转让区分而定。客观要件有三:股权转让已完成、出资期限已届至、受让人未按期足额缴纳出资。出让人补充责任范围受到以股权转让合同约定的未届期出资义务为限和以受让人未按期足额缴纳的出资部分为限双重限制。另外,出让人补充责任不受期限限制。

周期性边界下围岩热湿耦合传递特性及影响因素研究

为研究周期性边界下围岩热湿耦合传递特性,以相对湿度和温度为驱动势,建立了围岩热湿耦合传递数学模型,并设计正交试验,探究围岩热湿耦合传递特性的影响因素,得到了围岩年平均热湿吸放量及时长的预测公式。研究结果表明:围岩温湿度呈现季节性变化,围岩内部温湿度幅值存在延迟和衰减,越远离壁面其温湿度幅值越小,峰值温度越低且峰值出现的时间越晚;围岩调温圈厚度逐月增加,从1月厚度为5m到12月扩展至11m;年温度波幅对围岩吸放热量影响最大,年平均温度对吸放热时长影响最大,年湿度波幅对围岩放湿量影响最大,年平均湿度对围岩吸湿量及吸放湿时长影响最大。

未届出资期限股权转让股东补充责任合理性之检视——兼评《公司法(修订草案二审稿)》第八十八条第一款

全面认缴制下,未届出资期限股权转让中出资责任类型及其承担主体存在争议。《公司法(修订草案二审稿)》(以下简称《二审稿》)第八十八条第一款在《公司法(修订草案)》(以下简称《一审稿》)“股权受让股东担责”基础上增加“股权转让股东补充责任”符合股东出资义务与出资责任属性的理论前提,有益于股权转让股东逃避出资义务道德风险的防范及相关法律主体利益平衡。但对其补充责任合理性检视,在我国《民法典》与《公司法》视域下,股东出资义务转移的履行程序仍需进一步完善,股权转让股东承担补充责任也与认缴制改革目的有所偏离。针对《二审稿》第八十八条第一款,可以在一般情形下规定股权转让股东的补充责任,并以约定转让、发起人转让等情形承担其他类型出资责任为例外。

带有周期性微结构的微通道传热性能研究

为增强微通道热沉的散热性能,文章设计了一种带有周期性微结构的微通道,周期性微结构由通道中间的针肋与两侧的凹穴组成。采用数值模拟方法研究了不同结构形式与排布方式微结构对微通道传热性能的影响,利用强化传热因子评价其综合性能。结果表明,在所有微通道中,六边形肋交错渐密排布微通道展现出最佳的热性能和综合性能,相较于矩形微通道,在雷诺数为716.8时,其底面最高温度下降约25.46 K,热阻下降约54%,平均努塞尔数增大约45%,强化传热因子达1.503。

流过式介质电离质谱对郫县豆瓣酱香气物质的快速鉴别

为快速评价郫县豆瓣酱发酵过程中香气物质的差异性,利用流过式介质电离质谱(soft ionization by chemical reaction in transfer-mass spectrometry,SICRIT-MS)技术结合多元统计方法,对不同发酵时期的郫县豆瓣酱的香气物质进行了代谢组学研究。结果显示,SICRIT-MS完成单次检测仅需要1~3 s。此外,在质谱正离子模式下筛选了18个差异成分,负离子模式下11个差异成分。这些成分可以作为潜在的鉴别不同发酵时期豆瓣酱样品的特征标记成分。SICRIT-MS结合代谢组学技术为实现郫县豆瓣酱快速分级提供理论和技术支撑。

地铁车辆段上盖的全框支剪力墙结构设计探讨

根据地铁车辆段上盖全框支剪力墙结构设计实践,提出该结构按现行规范设计存在的问题,包括重力二阶效应验算,周期折减系数影响,框支柱剪力调整和厚板设计验算等问题。针对上述问题,建议重力二阶效应验算采用屈曲因子不小于20作为不考虑条件;少砌体墙的(框支)框架层考虑周期折减系数的影响,对(框支)框架层楼层剪力作折减;对于特一级或一级的框支柱的弯矩或剪力调整系数下调,避免调整后剪力远大于中震剪力的不合理情况;盖上剪力墙对厚板的冲切验算用作图法验算。

南运河冬季输水冰情及对策研究

南运河的冬季输水工作开展较少,冰期输水经验不足。2022—2023年度,南水北调东线北延输水为线路启用以来首次冬季输水。输水期间,在南运河段设立安陵、北陈屯2个观测站点,对冰期输水各个阶段的冰情特点进行观测,从而了解并掌握冰情的变化规律,并提出冰期输水对策,为今后的冰期输水工作提供参考。

Wave localization in randomly disordered periodic layered piezoelectric structures

Considering the mechnoelectrical coupling, the localization of SH-waves in disordered periodic layered piezoelectric structures is studied. The waves propagating in directions normal and tangential to the layers are considered. The transfer matrices between two consecutive unit cells are obtained according to the continuity conditions. The expressions of localization factor and localization length in the disordered periodic structures are presented. For the disordered periodic piezoelectric structures, the numerical results of localization factor and localization length are presented and discussed. It can be seen from the results that the frequency passbands and stopbands appear for the ordered periodic structures and the wave localization phenomenon occurs in the disordered periodic ones, and the larger the coefficient of variation is, the greater the degree of wave localization is. The widths of stopbands in the ordered periodic structures are very narrow when the properties of the consecutive piezoelectric materials are similar and the intervals of stopbands become broader when a certain material parameter has large changes. For the wave propagating in the direction normal to the layers the localization length has less dependence on the frequency, but for the wave propagating in the direction tangential to the layers the localization length is strongly dependent on the frequency.

Wave propagation control in periodic track structure through local resonance mechanism

Excessive vibration and noise radiation of the track structure can be caused by the operation of high speed trains.Though the track structure is characterized by obvious periodic properties and band gaps,the bandwidth is narrow and the elastic wave attenuation capability within the band gap is weak.In order to effectively control the vibration and noise of track structure,the local resonance mechanism is introduced to broaden the band gap and realize wave propagation control.The locally resonant units are attached periodically on the rail,forming a new locally resonant phononic crystal structure.Then the tuning of the elastic wave band gaps of track structure is discussed,and the formation mechanism of the band gap is explicated.The research results show that a new wide and adjustable locally resonant band gap is formed after the resonant units are introduced.The phenomenon of coupling and transition can be observed between the new locally resonant band gap and the original band gap of the periodic track structure with the band gap width reaching the maximum at the coupling position.The broader band gap can be applied for vibration and noise reduction in high speed railway track structure.

Band gap analysis of periodic structures based on cell experimental frequency response functions(FRFs)

An approach is proposed to estimate the transfer function of the periodic structure, which is known as an absorber due to its repetitive cells leading to the band gap phenomenon. The band gap is a frequency range in which vibration will be inhibited. A transfer function is usually performed to gain band gap. Previous scholars regard estimation of the transfer function as a forward problem assuming known cell mass and stiffness matrices. However, the estimation of band gap for irregular or complicated cells is hardly accurate because it is difficult to model the cell exactly. Therefore, we treat the estimation as an inverse problem by employing modal identification and curve fitting. A transfer matrix is then established by parameters identitled through modal analysis. Both simulations and experiments have been performed. Some interesting conclusions about the relationship between modal parameters and band gap have been achieved.