氧化碲声光偏转器的布拉格带宽和扫描线性问题

按声光偏转器的实际使用情况在入射光方向?₁固定不变的条件下求解反常布拉格绕射的Dixon方程,得到起作用超声方向?_a和绕射光方向?₂随频率f的变化关系。由?_a-f关系可精确决定声光偏转器的布拉格带宽和换能器长度等重要设计参数。所解出的?₂-f关系具有良好的线性,因而以往所作关于矫正扫描线性的探讨显得多余。 关键词：     

声光调制器在激光腔倒空技术中的应用

本文介绍了以36°Y切铌酸锂为换能器,以熔石英为声光互作用介质,驱动频率为389。5MHz的声光调制器的设计;计算并选定了换能器的各镀层厚度,研制成了用于激光腔内的中心频率389.5MHz声光脉冲调制器;叙述了该器件在同步泵浦染料激光器腔倒空技术中的应用。实验表明,当驱动平均功率约0.2W时,用该器件所实现的激光腔倒空的倒空比约40％。     

基于电光晶体马赫-曾德干涉仪的载波包络偏移频率调节方法

基于电光晶体马赫-曾德(M-Z)干涉仪的载波包络相位偏移频率(carrier-envelop offset frequency, f₀)调节方法是一种新颖的f₀调节方法.该方法通过改变脉冲包络而不改变载波频率实现对f₀信号的调节.本文对该方法所涉及的偏振控制装置进行了仿真,分析了其中波片光轴偏差对输出激光偏振方向和偏振度的影响.在实验上提出了一种光轴校准方法以减小波片光轴偏差带来的影响,并对比了抽运电流调节方法和基于电光晶体M-Z干涉仪的f₀调节方法对f₀信号和光梳与激光拍频信号(beat note, f_b)的影响.实验结果表明改变抽运电流,在f₀调节量为9 MHz的情况下,对f_b影响为7 MHz.而在相同f₀调节量下,电光晶体M-Z干涉仪f₀调节方法对f_b的影响为0.2 MHz,仅为抽运电流对f_b影响的1/35,从而验证了基...     

关于浅海声参量阵的应用

Westervelt远场参量阵理论表明,差频声压正比于它的降频比的平方,但对于近场,特别是到场点的距离比参量阵阵长小得可以忽略不计,但比发射换能器的瑞利长度大的情况下,结果应有所不同。本文将作者之一的理论用之于这种情况,得到了浅海参量阵的设计公式,这个公式给出的参量声压不是正比于f/f₀的平方,而是正比于R₀。此外,本文还对Moffett和Mellen的参量阵理论模型作了近似分析,得到了相同的设计公式,水池实验结果支持了本文的理论分析。 关键词：     

一种新型铕配合物的有机电致发光性能

研究了一种新型的稀土金属铕配合物EuL₁L₂的光致发光和电致发光特性。将这种铕配合物掺杂到PVK:PBD中,制备成结构为ITO/PVK:PBD:EuL₁L₂/PBD/Alq₃/Mg:Ag/Ag的器件,对其电致发光性能进行研究,发现Eu³⁺离子和Alq₃的相对发光强度随PVK:PBD:EuL₁L₂和Alq₃之间的激子阻挡层PBD的厚度变化而变化,通过调节PBD的厚度,得到了色纯度较高的红色电致发光器件,其光谱具有显著的Eu³⁺离子的光谱特征。     

W型六角铁氧体的磁晶各向异性

本文根据晶场理论用点电荷近似计算了Zn₂-W六角铁氧体七个晶位(2d,4e,4f_Ⅳ,4f_Ⅵ,6g,12k和4f)Fe³⁺离子的单离子各向异性。结果正如我们所预期的,各个晶位都有一定贡献,且既有正的贡献,也有负的贡献,能够解释对Zn₂-W作离子置换的实验结果。 关键词：     

拓扑绝缘体基铁磁/f-波超导隧道结Andreev反射研究

基于Bogoliubov-de Gennes方程和Blonder-Tinkham-Klapwijk理论研究了三维拓扑绝缘体基铁磁/各向异性f-波超导隧道结的Andreev反射,其中f-波超导体选取f₁和f₂-波两种配对势.研究发现,对于f₁和f₂波,铁磁体中的磁能隙可以增强传统的Andreev逆向反射,但对Andreev镜面反射有抑制作用;但随着施加在超导体顶部电极上的栅极电位的增加,两种类型的反射都会增强.通过改变磁能隙,可以调节两种反射在准粒子输运过程中占有优势的程度.这些结果提供了一种实验检测拓扑绝缘体薄膜中镜面Andreev反射的方法.此外,隧穿电导和散粒噪声谱的差异可用于区分f₁和f₂波配对势.     

功能层厚度对叠层有机电致发光器件出光性能影响的数值研究

功能层厚度是影响有机电致发光器件出光效率的主要因素之一,故获得不同功能层厚度对器件出光特性的影响规律是制备高性能器件的重要基础. 本文基于薄膜光学原理、电偶极子辐射理论及Fabry-Pérot微腔原理,建立了结构为glass/ITO/N,N0-bis（naphthalen-1-yl）-N,N0-bis（phenyl）-benzidine（NPB）/tris（8-hydroxyquinoline）aluminum（Alq₃）/molybdenum trioxide（MoO₃）/NPB/Alq₃/Al的叠层有机电致发光器件的光学模型,系统地研究了各个功能层厚度对叠层有机电致发光器件出光强度的影响,得到了功能层厚度对器件出光强度影响的规律. 该模型的建立与所获得的结果可对深入了解叠层有机电致发光器件的工作机理以及制备高性能的器件提供一定的帮助. 关键词： 叠层有机发光器件 出光特性 厚度 数值研究     

The Φp bound state in the unitary coupled-channel approximation

The strong attractive interaction of the Φ meson and the proton has recently been reported by the ALICE Collaboration.The corresponding scattering length f₀ is given as Re(f₀)=0.85±0.34(stat)±0.14(syst) and Im(f₀)=0.16±0.10(stat)± 0.09(syst) fm.The fact that the real part is significant in contrast to the imaginary part indicates a dominant role of elastic scattering,whereas the inelastic process is less important.In this work,such scattering processes are inspec...     

MgB2超导膜的厚度与其Jc(5K,0T)的关系

通过混合物理化学气相沉积法 (hybrid physical-chemical vapor deposition, HPCVD), 在(000l) SiC 衬底上制得一系列从10 nm到8 μm的MgB₂超导膜样品, 并对它们的形貌、超导转变温度T_c 和临界电流密度J_c与膜厚度的关系进行了研究. 观察到T_c随膜厚度增加上升到最大值后, 尽管膜继续增厚, 但T_c值保持近乎平稳, 而J_c则先随膜厚度增加上升到最高值后, 继而则随膜的厚度的增加而下降. MgB₂膜的T_c(0)和T_c(onset)值与膜厚的关系基本一致, T_c(0)在膜厚为230 nm处达到最大值T_c(0)=41.4 K, 而J_c(5K,0T)在膜厚为100 nm时达到最大值, J_c (5 K, 0 T)=2.3×10⁸A·cm^-2, 这也说明了我们能用HPCVD方法制备出高质量干净MgB₂超导膜. 本文研究的超导膜厚度变化跨度非常大, 从10 nm级的超薄膜到100 nm级的薄膜, 再到几微米的厚膜, 如此T_c和J_c对膜厚度变化的依赖就有了较完整、成体系的研究. 并且本文的工作对MgB₂超导薄膜制备的厚度选取具有实际应用意义. 关键词： 2超导膜')" href="#">MgB₂超导膜 混合物理化学气相沉积法 厚度 临界电流密度     

Lead-free BNBT-6 piezoelectric ceramic fibre/epoxy 1-3 composites for ultrasonic transducer applications

Barium-modified bismuth sodium titanate, 0.94 ×(Bi_0.5Na_0.5)TiO₃-0.06BaTiO₃ (BNBT-6), fine-scale piezoelectric fibres were fabricated using a viscous suspension spinning process (VSSP). The sintered BNBT-6 fibres with diameters of 300 m were fabricated into 1-3 composites with fibre volume fraction v_f of 0.2–0.5. Piezoelectric and dielectric properties of the 1-3 composites were measured. The electromechanical coupling coefficient k_t of a v_f=0.40 composite is 0.52. Properties of the VSSP fibres were calculated using the measured properties of the 1-3 composites. A v_f=0.40 composite was thinned down to 213-m thickness and constructed into an ultrasonic transducer. The pulse-echo response, bandwidth and insertion loss of the transducers were studied. The VSSP fibre composite transducer with v_f=0.40 has a centre frequency of 7 MHz with a bandwidth of 88%. The good performance indicated that the BNBT-6/epoxy 1-3 fibre composite transducer has potential for medical imaging applications. PACS 77.84.Dy; 77.84.Lf; 43.38.+n     

Generalized Wagner’s diffusion model of surface modification of materials by plasma diffusion treatment

0 f^-1(t/t₀), where g(t) is the sub-layer thickness at time t, g₀ and t₀ are parameters that depend on the treated material and plasma characteristics, and f^-1 is the inverse function of f(x)=-(ln(1-x)+x), where x=g(t)/g₀, 0≤x≤1. Under negligible erosion effects, the model becomes of Wagner’s diffusion model type and the expression for g(t) reduces to the parabolic law. The model can be simplified by considering the compound layer as a united one. The general and simplified models can be used as a method for the experimental determining of the effective diffusion coefficients and the erosion rate during plasma treatment of material surfaces. Received: 26 February 1998/Accepted: 15 March 1998     

高维宇宙中标量粒子的非热分布和总熵的增加

本文讨论了宇宙处于高维相时无质量标量粒子气的非热分布、能密度以及增加的熵。从迅变阶段粒子数分布不变的假定出发,在初始温度β₀^-11/2α₂₀^-1的近似下,计算得高维相结束时的总熵与初始总嫡之比S_f/S₀与T₀α₂₀/T_fα_2f同量级。S_f,T 关键词：     

一维单峰映象的拓扑熵

在对Logistic映象数值计算的基础上,我们分析了一维单峰映象的逆轨道结构,证明了不同参数处逆轨道总数N(n)随求逆次数n而变化的递推公式。借此解析地求得了在倍周期区中h(f)≡0;在U序列RLR²¹的m=3+2l周期点上h(f)=logα_mp,其中α_mp为方程α^m-2α^m-2-1=0的最大实根;在2^j-1常和2j带交界处h_j(f)=(1/2)^jlog2,由此可得聚点μ_∞处拓扑熵的标度指数t=0.449806…。在此基础上,我们还求得了混沌区的周期窗口,U序列RL^aR^b所对应的各点处的拓扑熵,以及h_R*Q(f)=(1/2)h_Q(f)的关系。证明是在M.S.S.规则和“*”乘法则的基础上进行的。所以本文的结果对一维单峰映象是普适的。 关键词：     

Quark-gluonium content of the scalar-isoscalar states f0(980), f0(1300), f0(1500), f0(1750), and f0(1420 ?70+150 ) from hadronic decays

On the basis of the decay couplings f ₀ → ππ, K , ηη, ηη′ found earlier in the study of analytical (IJ ^PC =00⁺⁺) amplitude in the mass range 450–1900 MeV, we analyze the quark-gluonium content of the resonances f ₀(980), f ₀(1300), f ₀(1500), and f ₀(1750) and the broad state f ₀(1420 ₋₇₀ ⁺¹⁵⁰ ). The K-matrix technique used in the analysis makes it possible to evaluate the quark-gluonium content both for the states with switched-off decay channels (bare states, f ₀ ^bare ) and for the real resonances. We observe a significant change in the quark-gluonium composition in the evolution from bare states to real resonances, which is due to the mixing of states in the transitions f ₀(m ₁) → real mesons → f ₀ (m ₂) responsible for the decay processes as well. For f ₀(980), the analysis confirmed the dominance of q component, thus proving the n /s composition found in the study of the radiative decays. For the mesons f ₀(1300), f ₀(1500), and f ₀(1750), the hadronic decays do not allow one to determine uniquely the n , s , and gluonium components, providing relative percentage only. The analysis shows that the broad state f ₀(1420 ₋₇₀ ⁺¹⁵⁰ ) can mix with the flavor singlet q component only, which is consistent with gluonium origin of the broad resonance. From Yadernaya Fizika, Vol. 66, No. 4, 2003, pp. 772–785. Original English Text Copyright ? 2003 by Anisovich, Nikonov, Sarantsev. This article was submitted by the authors in English.     

Experimental study of the ultrasonic transducer non-linear vibrations

Conclusion The method introduced proved to be useful in obtaining information on transducer behaviour at high power levels. With respect to ultrasonic generator design several conclusions may be drawn from the transducer characteristics. First, it was found that the current and the pick-up voltage characteristics are equivalent with respect to the information content on the transducer vibrations. Therefore, the feedback signal may be derived both from the currentI and from the voltageU _p .It was also found that the resonance frequency of the transducerf _r varies strongly both with the power level and with the mechanical load. However, it is the resonance phase angle _r that is almost independent of these external changes.Lastly, because of the jumps, the transducer may be tuned to the resonance only by lowering the frequencyf starting from an arbitrary frequency higher thanf ₁. In designing a feedback system this requirement should be taken into account.The author wishes to thank M. Los and L. Kozák from the Ultrasonic Laboratory of the Czech Technical University in Prague for kindly lending him the ultrasonic transducer for this study.     

Effect of the area of a lithium niobate transducer on the efficiency of ultrasonic atomization driven by resonance vibration

In recent years, individual control of one’s personal environment has been drawing increasing attention due to the growing interest in health care. Wearable devices are especially useful because of their controllability regardless of location. Humidity is one of the inevitable factors in the personal environment as a preventive against infectious diseases. Although atomization devices are commonly used as a method of humidity control, at present, there are no wearable humidity control devices. Vibration of a lithium niobate (LN) device in the thickness mode is a promising piezoelectric method for miniaturization of atomization devices for humidity control. To miniaturize the atomization device, the transducer size needs to be small not so much as to decrease the atomization efficiency. However, the effect of the device area on the atomization efficiency of LN at a size suitable for mounting in wearable devices has not been studied. Here, we conducted an atomization demonstration of LN devices with different sizes to evaluate particle size and atomization efficiency. Furthermore, to reveal the relationship between vibration behavior and atomization efficiency, resonance vibration in the MHz frequency band was evaluated by the finite element method and an impedance analyzer. The results showed that the peak size of water particles atomized by each device was in the range of 3.2 to 4.2 µm, which is smaller than particles produced by typical piezoelectric ceramics. Moreover, the best LN size for efficient atomization was found to be 8 mm × 10 mm among the five LN device sizes used in experiments. From the relationship between vibration behavior and atomization efficiency, the size of the transducer was suggested to affect the vibration mode. The obtained result suggested that the LN device is suitable for small wearable nebulizer devices.     

Resonances in 1-3 piezocomposite rings

Lead zirconate titanate (PZT)/epoxy 1-3 piezocomposite rings with PZT volume fraction φ ranging from 0.58 to 0.93 have been fabricated. They have sufficiently small epoxy width (∼77–81 μm) and can be treated as effective homogeneous media. Stopband resonances (f_S1, f_S2) can be observed in the spectra and their locations are close to the theoretical predictions. Mode coupling theory and a finite element model (FEM) are applied to estimate the thickness (f_T), lateral (f_L), radial (f_R), and wall-thickness (f_W) resonances of the composite rings. As the frequencies and electromechanical coupling coefficients play a significant role in the performance of a composite transducer, it is important to know how these parameters change with φ. Good agreements are found between the experimental results and the FEM simulations. It is observed that the f_R and f_W vibrations greatly deteriorate at low values of φ. To avoid unwanted modes from coupling to f_T, the thickness and aspect ratio of the PZT elements in the rings should be optimized. By using the FEM, effects of the ring dimensions on the lateral resonances can be predicted. PACS 77.84.Lf; 81.05.-t     

德拜特征温度的各向异性与非均匀性

由于德拜特征温度标识着原子或离子在晶体内的平均振动能量,而不同原子在晶体内的振动模式,或同一原子在非立方晶体内的振动模式显然不同,这就发生了特征温度的非均匀性及各向异性问题。本文提出了从粉末X射线衍射强度测定晶体特征温度的非均匀性及各向异性的方法。测定了CaF₂的特征温度。结果发现:Ca²⁺离子在CaF₂晶体内的特征温度为400K,而F^-离子的特征温度为476K,二者相差76K。 关键词：