A novel evacuation passageway formed by a breathing air supply zone combined with upward ventilation

With the development of transportation, the tunnel has become one of the important facilities of railway, highway and subway transportation. However, fire hazards occurring inside the tunnel may incur huge numbers of casualties and property losses. In this paper, a breathing air supply zone combined with an upward ventilation assisted tunnel evacuation system (BTES) is introduced. It can be used to create a safe, smoke-free evacuation passageway out of the tunnel. The BTES is optimized to achieve high-performance. The impacts of heat release rates, fire source locations and fire detection times are also discussed.     

Terfenol-D/Pb(Zr,Ti)O3 Disk-Ring Multiferroic Heterostructures Coupled Through Normal Stresses

Disk-ring multiferroic heterostructures composed of Terfenol-D and Pb(Zr,Ti)O₃ (PZT) were prepared and characterized, for which the ferromagnetic and ferroelectric phases were coupled through normal stresses instead of the shear stresses that acted in most of the previous multiferroic heterostructures. High low-frequency magnetoelectric coefficients of 0.10–0.75 V cm⁻¹ Oe⁻¹ were attained for the disk-ring heterostructures, which indicated the strong magnetoelectric coupling. Moreover, a symmetrical resonant peak was observed for dE ₃/dH ₃ in the frequency range of 1–200 kHz, while another weak peak with asymmetrical shape also existed at a lower frequency for dE ₃/dH ₁, which was due to the combination of two vibration modes.     

Circular polarized electronically-controlled antenna array based on CRLH-TL

In this paper, a circular polarized electronically-controlled scanning microstrip antenna array is designed, which is based on composite right left-handed transmission line (CRLH TL) and is realized by varactor diodes. Proposed electronically-controlled antenna arrays till now are always linear-polarized as the axial ratio (AR) may be spoiled by the DC feed line, especially in the CRLH TL based case. A more separated CRLH TL integrated with active lumped elements is utilized to solve the problem. The antenna array is composed of the CRLH microstrip transmission line structure and circular polarized microstrip antenna. The direction of the main lobe varies from ?1° to ?20 ° by continuously modifying the varactor diodes bias voltages from 0 to 20 V with 5 V as a step. The AR remains below 3 dB in the scanning range. The simulation and experimental results show a good consistence.     

Negative slope of resistivity–temperature curve and positive magnetoresistance in antiperovskite ZnCNi3−x Mn x (1.15≤x≤1.5)

In antiperovskite intermetallics ZnCNi_3?x Mn _x , the negative slope coefficient (NSC) dρ/dT of resistivity–temperature curves is observed when x=1.15,1.25,1.4,1.5. The sample with x=1.25 shows a semiconductor-like behavior in the whole temperature range of 15–290 K. By study of the magnetization, magnetoresistance, and low-temperature X-ray diffraction, it is found that Mn dopant significantly affects the physical properties of ZnCNi_3?x Mn _x by changing both the carrier density and the magnetism. The origin of the NSC dρ/dT can be ascribed to the change of hole-like carrier density, which is adjusted by Mn content. The existence of hole-like carriers can be understood rationally by the two-band model. The change of sign of magnetoresistance from positive to negative has been observed in ZnCNi_3?x Mn _x with the change of Mn content, which could be ascribed to the competition between the contribution from field-induced suppression of the thermally excited ferromagnetic spin fluctuations and the Lorentz contribution. When Mn content is low, the Lorentz contribution dominates the sign of magnetoresistance. On the other hand, when Mn content is high, the contribution from field-induced suppression of the thermally excited ferromagnetic spin fluctuations dominates the sign of magnetoresistance.     

EAST上基于端口密度测量的低杂波耦合研究

介绍了一套安装在EAST装置低杂波天线端口上方,用来测量端口附近电子密度的Langmuir三探针系统及其初步实验结果。此探针系统由探针、测量电路、数据采集以及数据处理四部分构成。实验结果表明：在低杂波天线端口充气的条件下,低杂波注入后端口密度会有明显的增加。端口密度与反射系数的关系与理论趋势一致,EAST上低杂波耦合的最佳密度出现在4~5×10¹⁷m^-3。     

周期量级激光脉冲在不同密度的原子介质中传播行为的比较(英文)

利用不含慢变包络近似和旋波近似的全波Maxwell-Bloch方程组的数值解,研究了周期量级超短激光脉冲在Ladder型三能级原子介质中的传播行为并与在相应的稀疏介质中的情况进行了比较.我们发现,在传播过程中,超短脉冲在稠密介质中的时间演化规律与在稀疏介质中明显不同,而且这种差别将随初始脉冲面积的增大而加大.当初始脉冲面积较小时,在传播过程中,脉冲形状在稀疏介质中只有小的改变而在稠密介质中却有显著的变化.当初始脉冲面积足够大时,在稠密介质中在不同的传播距离处脉冲分裂为不同数量和形状的亚脉冲;在稀疏介质中脉冲形状在传播过程中仍然只有小的改变。产生以上差别的原因在于稠密原子介质中近偶极-偶极(NDD)相互作用导致的局域场修正(LFC)及比稀疏原子介质更强的极化电场的影响.其中,更强的极化电场的影响起着主要的作用,但局域场修正的作用也不能忽略,而极化电场的增强是由于原子密度的增加.     

苹果盛果期冠层高光谱与其组分特征的定量模型研究

从分析苹果树盛果期冠层高光谱入手,结合同一时间的数码照片,在Erdas,ViewSpec Pro,DPS和LIBSVM等软件的支持下,采用相关分析、线性回归、逐步回归、基于BP人工神经网络分析、支持向量机回归方法,探析高光谱反射率及其转换数据与冠层组分指数间的关系。结果表明,冠层反射率受地表反光膜的影响显著;原始反射率与果叶比的相关性最好,611~680 nm为反映两者关系的特征波段;在特征波段内,依据原始反射率和果叶比所建立的4种模型都可满足预测需要,但基于BP人工神经网络模型和支持向量机回归模型整体上优于一元线性回归模型和多元线性回归模型,尤以支持向量机回归模型精度最高。研究结果可为后续的苹果遥感估产工作提供理论支持。     

基于VISA的PXI设备访问新方法

由于PXI设备的灵活性,在访问过程中需要用户参与到配置过程中。为了方便用户,并增强PXI设备访问的安全性和准确性,避免系统因用户配置问题导致的功能异常,提出了一种基于VISA的以PXI设备串号为基础的设备访问方法。通过将PXI设备的串号信息固化在PXI设备的配置寄存器中,根据设备串号信息自动获得设备资源描述符,进而对设备进行访问。实际应用表明,该方法能够完成对PXI设备的访问,避免了用户的配置过程,实现了PXI设备资源的自动配置,增强了设备访问的安全性和准确性,具有良好的实际应用价值。     

Weighted Composition Operators from the Bloch Spaces to Weighted Hardy Spaces on Bounded Symmetric Domains*

Let B_E be a bounded symmetric domain realized as the unit open ball of JB*-triples.The authors will characterize the bounded weighted composition operator from the Bloch space B(BE) to weighted Hardy space H_v^∞ in terms of Kobayashi distance.The authors also give a sufficient condition for the compactness,and also give the upper bound of its essential norm.As a corollary,they show that the boundedness and compactness are equivalent for composition operator fromB(B...     

Energy and Quadratic Invariants Preserving Methods for Hamiltonian Systems with Holonomic Constraints

We introduce a new class of parametrized structure--preserving partitioned Runge-Kutta ($\alpha$-PRK) methods for Hamiltonian systems with holonomic constraints. The methods are symplectic for any fixed scalar parameter $\alpha$, and are reduced to the usual symplectic PRK methods like Shake-Rattle method or PRK schemes based on Lobatto IIIA-IIIB pairs when $\alpha=0$. We provide a new variational formulation for symplectic PRK schemes and use it to prove that the $\alpha$-PRK methods can preserve the quadratic invariants for Hamiltonian systems subject to holonomic constraints. Meanwhile, for any given consistent initial values $(p_{0}, q_0)$ and small step size $h>0$, it is proved that there exists $\alpha^*=\alpha(h, p_0, q_0)$ such that the Hamiltonian energy can also be exactly preserved at each step. Based on this, we propose some energy and quadratic invariants preserving $\alpha$-PRK methods. These $\alpha$-PRK methods are shown to have the same convergence rate as the usual PRK methods and perform very well in various numerical experiments.