盾构作业区域湿热环境的研究

通过对掘进中的盾构及隧道内的温度和湿度的实地测量,本文针对盾构施工过程中在其作业区域存在的高温高湿等恶劣的工作环境问题,就其形成的原因和热湿传递的特性进行了分析,还对其中的流场进行了初步的数值模拟,提出了改善盾构作业区域内工作环境的措施。     

非稳态横掠管束周期性充分发展对流换热的数值模拟

本文采用非稳态数学模型对横掠管束的周期性充分发展流动与换热进行了数值模拟。结果显示,在所考虑的参数条件下,Re≥100以后流场和温度场随时间发生振荡,并且振幅随Re增加而增大;进一步增加Re到一定值后,在管束间会有交替出现的涡。计算得到的平均Nusselt数与现有文献中的实验关联式基本是吻合的。平均Nusselt数的计算值随流动方向管间距的增加而增加。     

Optodynamic analysis of direct laser writing of graduation lines

The direct laser writing of graduation lines in Cr thin films on glass substrates has been investigated. The Nd-YAG laser and the astigmatic optical system have been used to write rectangular holes in the Cr film. The optimal writing parameters: the laser pulse energy, the Cr layer thickness and the substrate-objective distance were determined using the optoacoustic probe beam deflection method to detect the evaporation of the material. The evaporation is concluded to be the essential process in the laser writing of graduation lines. The rims formed by the surface tension gradient at the hole edges indicate that the laser writing of graduation lines is a typical two-phase removal process.     

Cavity-dumped electro-optical Q-switched Nd:GdVO4 laser with high repetition rate

We reported a cavity-dumped operation of electro-optical Q-switched Nd:GdVO₄ laser at high repetition rates for the first time. A constant 5.5 ns pulse duration was realized. The maximum average output power was 5.1 W at the highest repetition rate of 50 kHz, corresponding to a peak power of 18.5 kW.     

Table-like magnetocaloric effect and enhanced refrigerant capacity in crystalline Gd55Co35Mn10 alloy melt spun ribbons

Gd₅₅Co₃₅Mn₁₀ ribbons were prepared by melt-spinning and subsequent crystallization treatment. Crystallization resulted in the precipitation of the Gd₃Co-type and Gd₁₂Co₇-type phases in the amorphous matrix. Under a magnetic field change of 0–5 T, a table-like magnetocaloric effect, with a maximum magnetic entropy change ${(?\mathrm{\Delta }{S}_{\mathrm{M}})}^{\max }$ of $5.46\text{J}{\text{kg}}^{?1}{\text{K}}^{?1}$ in the temperature range of 137–180 K and enhanced refrigerant capacity (RC) of $536.4\text{J}{\text{kg}}^{?1}$, was achieved in Gd₅₅Co₃₅Mn₁₀ ribbons crystallized at 600 K for 30 min. The table-like ${(?\mathrm{\Delta }{S}_{\mathrm{M}})}^{\max }$ feature and enhanced RC values make Gd₅₅Co₃₅Mn₁₀ crystallized ribbons promising for Ericsson-cycle magnetic refrigeration in the temperature range from 137 to 180 K.     

三维方腔内竖直平板自然对流的数值模拟

三维方腔内竖直平板自然对流的数值模拟杨沫，李少华，徐志明，杨善让（东北电力学院动力系吉林１３２０１２）陶文铨（西安交通大学动力系西安７１００４９）关键词封闭腔；自然对流；数值模拟１引言三维封闭腔内孤立物体的自然对流换热在工程上具有广泛应用背景。例如；...     

多层膜磁性微泡的非线性声振动特性

超顺磁性氧化铁纳米粒子与造影剂微泡结合形成磁性微泡,用于产生多模态造影剂,以增强医学超声和磁共振成像.将装载有纳米磁性颗粒的微泡包膜层看作由磁流体膜与磷脂膜组合而成的双层膜结构,同时考虑磁性纳米颗粒体积分数a对膜密度及黏度的影响,从气泡动力学基本理论出发,构建多层膜结构磁性微泡非线性动力学方程.数值分析了驱动声压和频率等声场参数、颗粒体积分数、膜层厚度以及表面张力等膜壳参数对微泡声动力学行为的影响.结果表明,当磁性颗粒体积分数较小且a≤0.1时,磁性微泡声响应特性与普通包膜微泡相似,微泡的声频响应与其初始尺寸和驱动压有关;当驱动声场频率f为磁性微泡共振频率f0的2倍(f=2f0)时,微泡振动失稳临界声压最低;磁性颗粒的存在抑制了泡的膨胀和收缩但抑制效果非常有限;磁性微泡外膜层材料的表面张力参数K及膜层厚度d也会影响微泡的振动,当表面张力参数及膜厚取值分别为0.2—0.4 N/m及50—150 nm时,可观察到气泡存在不稳定振动响应区.     

Bidirectional Controlled Joint Remote State Preparation via a Seven-Qubit Entangled State

A new protocol for implementing five-party bidirectional controlled joint remote state preparation is proposed by using a seven-qubit entangled state as the quantum channel. It can be shown that two distant senders can simultaneously and deterministically exchange their states with the other senders under the control of the supervisor, and it cannot be succeed without permission of the controller. Only pauli operation and single-qubit measurement are used in our scheme, so the scheme with five-party is feasible within the reach of current technologies.     

蒸发冷却的管外换热性能的实验研究

将淋水填料与盘管组合,构成高效低耗的密闭式冷却塔,成为当前闭式塔的主流塔型.本文以此类设备的研发为背景,设计了一个用于蒸发冷却换热模块性能试验的小型风筒,在横流和逆流模式下就单纯管束换热模块与填料-管束结合型换热模块的管外换热性能进行了比较,并研究了淋水密度、风量对其换热性能的影响.试验表明,采用填料-管束结合型换热模块,在相同截面风速和淋水密度以及相同的控制壁温和空气湿球温度条件下,管外综合换热系数比单纯管束有明显提高;对相同换热模块,管外综合换热系数在试验范围内随淋水密度和截面风速的增大而增大.     

偏最小二乘法在火焰原子吸收分析中的应用

本文用偏最小二乘法校正了火焰原子吸收分析中Ｐｄ２４７．４３ｎｍ对Ｐｂ２４７．６３８ｎｍ的吸收线重叠干扰，对合成样中Ｐｂ和Ｐｄ的测定，结果令人满意，ＰＬＳ法是谱线重叠干扰的有效校正方法。