Weak amplification of the magnetocaloric effect in manganites

The magnetocaloric effect (MCE) has been measured by direct method in La_0.8Ag_0.15MnO₃ and La_0.85Ag_0.15MnO₃ before and after coating of Fe–Co layer on the surfaces of manganites. An evaporated film thickness has been 500 nm. The measurements have shown the MCE to be increased by 7%–8% under 26 kOe after Fe–Co coating on the flat surfaces.     

ps参量放大效应

本文报道用0.53μm波长超短脉冲序列泵浦角度调谐的LiNbO_3参量晶体,获得1%单程参量放大能量转换效率,并在0.8～1.6μm范围测得参量信号光和空载光波长调谐曲线.     

等离子体密度对激光拉曼放大机理的影响

等离子体中的背向拉曼散射机理可以用来产生超短超强的激光脉冲. 本文采用粒子模拟方法模拟研究了等离子体密度对激光拉曼放大过程的影响. 研究发现, 过低的等离子体密度会导致等离子体波提前波破而降低能量转换效率; 而过高的等离子体密度又会导致其他不稳定性的快速增长, 限制作用距离和输出能量. 因此, 拉曼放大机理的最佳等离子体密度应处于等离子体波破的密度阈值附近, 可以获得最高的能量转换效率和能量输出. 另外, 空间频谱分析显示放大激光的强度饱和主要来自于自相位调制不稳定性的发展. 利用10¹³ W·cm^-2的抽运激光脉冲, 模拟证实拉曼放大机理可有效地将种子激光的强度从10¹³ W·cm^-2 放大到10¹⁷ W·cm^-2, 脉宽压缩到40 fs, 且能量转换效率达到58%.     

Quantum effect on parametric amplification characteristics in piezoelectric semiconductors

Using QHD model the parametric interaction of a laser radiation in an unmagnetised piezoelectric semiconductor has been studied. It is found that the Bohm potential in the electron dynamics enhances the gain coefficient of parametrically generated modes whereas reduces the threshold pump intensity.     

单粒子瞬变中的双极放大效应研究

采用三维数值模拟的方法对比研究了单个NMOS晶体管和反相器链中的单粒子瞬变（single event transient,SET）电流脉冲,发现深亚微米工艺下双极放大电流在单管的SET电流脉冲中占主要成分,而在反相器链的SET模拟中不明显,分析二者的区别解释了源/体结偏压的形成过程和放大机理,并证明了双极放大效应受源/体结偏压影响的结论.在此基础上分析了NMOS管中源极的正向电流及其机理,发现台阶区的源极正向电流主要是由扩散作用形成的. 关键词： 单粒子瞬变 双极放大 混合模拟 台阶区电流     

Resonant amplification of the magnetoelectric effect in ferrite-piezoelectric composites

The magnetoelectric effect in ferrite-piezoelectric composites is considered. A theory of the magnetoelectric effect in the electromechanical-resonance region for disk-shaped samples is presented. The magnetooptical coefficient is calculated for longitudinal and transverse orientations of electric and magnetic fields. It is shown that the effect increases by a few orders of magnitude at the electromechanical-resonance frequency. The frequency dependence of the effect is experimentally studied for a ferrite-nickel spinel-PZT composite. A resonant increase in the effect is observed (in agreement with the theory); the highest value of the magnetoelectric coefficient was 15 V/(cm Oe).     

玻色凝聚原子云的二次干涉及其放大效应

捕限在三维轴对称谐振势阱叠加一维光晶格势的组合势中的玻色凝聚气体，取消磁阱和光晶格势后，将形成沿轴向向两侧运动的干涉边峰.提出一个新的实验方案，使这样的干涉边峰再次相遇叠加，以探讨物质波的二次干涉效应.研究表明，在干涉边峰相干加强的区域，玻色凝聚原子云的密度会得到有效放大.基于现有的实验技术，这个新实验是可以实现的，这种效应也是可以观测得到的.     

双折射光纤中拉曼效应对参量放大增益谱的影响

根据激光脉冲在光纤中传输时, 所满足的波动方程, 导出了拉曼效应和参量放大共同作用下, 在双折射光纤中所遵循的耦合模方程, 并引入平行拉曼增益的洛伦兹模型, 给出了输入抽运波偏振方向同双折射轴成45^o 时, 拉曼效应和参量放大共同作用所导致的增益. 讨论并分析了拉曼效应在不同色散区对参量放大增益谱的影响. 结果表明, 在考虑拉曼效应后, 使得参量放大斯托克斯波与反斯托克斯波增益谱彼此不对称; 在反常色散区, 产生的增益以反斯托克斯波为主, 正常色散区则以斯托克斯波为主.     

Non-local effect in Brillouin optical time-domain analyzer based on Raman amplification

应用包含探测光、布里渊泵浦光及拉曼泵浦光相互作用理论模型,数值分析了基于拉曼放大的长距离布里渊光时域分析仪非局域化特性.结果表明:非局域化随探测光及拉曼泵滴功率增加而恶化;通过频分复用(将具有不同布里渊频移的光纤拼接)及时分复用技术(同时对布里渊泵浦及探测光进行脉冲调制),可有效缩短布里渊泵浦与探测光的作用距离,达到较理想的抑制非局域效应结果.     

Non-classical effect of quantum non-demolition measurement in presence of parametric amplification

A full quantum treatment of the problem of quantum non-demolition measurements in non-linear optical media is considered. The system consists of four different coupling parameters in addition to different phase parameters. The solution of the Heisenberg equations of motion for the dynamical operators is obtained. The phenomenon of squeezing is examined for both normal and principal squeezing and it has been shown that it is more pronounced for the compound mode case. The intensity correlation function is also calculated and discussed where the observation of the antibunching can be reported. In addition to the higher-order moments we examined the quantum correlation functions, joint quasidistribution functions, as well as photon-number distribution and its factorial moments. It has shown that the non-classical properties is apparent of this system and more pronounced for the compound mode (1,3).     

拉曼放大布里渊光时域分析系统非局域效应

应用包含探测光、布里渊泵浦光及拉曼泵浦光相互作用理论模型,数值分析了基于拉曼放大的长距离布里渊光时域分析仪非局域化特性。结果表明：非局域化随探测光及拉曼泵浦功率增加而恶化;通过频分复用(将具有不同布里渊频移的光纤拼接)及时分复用技术(同时对布里渊泵浦及探测光进行脉冲调制),可有效缩短布里渊泵浦与探测光的作用距离,达到较理想的抑制非局域效应结果。     

The effect of large openings on cavity amplification at ultrasonic frequencies

It is sometimes desired to exploit acoustic amplification in a cavity that is not entirely enclosed. Because of the presence of openings in the cavity, acoustic energy will leave the cavity and degrade the degree of amplification. The extent of this problem is unknown when the size of the openings becomes large relative to a wavelength. The present paper describes a quantitative estimation of the effect of large openings on the amplification performance of an acoustic cavity. Air was assumed to be the working medium. The amplification taking place in a rigid-walled rectangular channel excited by a transducer flush-mounted in one wall was compared to the amplification that would take place in a bounded rectangular resonator excited by the same transducer. It was found, for frequencies in the range 25 kHz-1 MHz, that source ka's greater than 37 and 42 were required in order for the collimation of the transducer beam to overcome the leakage of acoustic energy through the openings for one- and two-half wavelength resonances, respectively. Experimental measurements conducted over source ka's ranging from 6.5 to 26.1, resulted in quality factors 8%-18% lower than theoretically predicted values for one-, two-, and three-half wavelength resonances.     

双折射色散阶跃光纤中拉曼效应和参量放大增益谱

在拉曼效应和参量放大共同作用下,当激光脉冲在双折射光纤中传输时,根据所遵循的耦合模方程,通过引入平行拉曼增益的洛伦兹模型,导出了当输入泵浦波偏振方向同双折射轴成45°角时,在双折射色散阶跃光纤中拉曼效应和参量放大共同作用所导致的增益,讨论并分析了在不同色散区增益谱随相关参量的变化。结果表明:由于拉曼效应、参量放大、双折射和色散的相互作用,导致增益谱的斯托克斯波与反斯托克斯波彼此不对称;在反常色散区,产生的增益以反斯托克斯波为主,在正常色散区则以斯托克斯波为主;当表征距离的级数m发生变化时,增益谱也随之发生变化,可以利用色散阶跃光纤在适当的级数m位置提取T频率脉冲。     

带延时光学双稳装置分岔点处的光放大效应

调节在倍周期分岔第一个分岔点处的带延时光学双稳装置(OBD),对与系统谐振的光学小信号具有放大作用.本文对此作了理论分析.     

The effect of voice amplification on occupational vocal dose in elementary school teachers

Two elementary school teachers, one with and one without a history of vocal complaints, wore a vocal dosimeter all day at school for a 3-week period. In the second week, each teacher wore a portable voice amplifier. Each teacher showed a reduction in vocal intensity during the week of amplification, with a larger effect for the teacher with vocal difficulties. This teacher also showed a decrease in hourly vocal fold distance dose as measured by the dosimeter despite incurring longer phonation times. Fundamental frequency and vocal fold cycle dose did not appear to be affected by the use of amplification during the teaching day. Both teachers showed evidence of a possible moderate effect of adjusting vocal intensity in the week after amplification, possibly as a means to recalibrate their perceived vocal loudness. This study demonstrates the usefulness of both vocal dosimetry and amplification in monitoring and modifying vocal dose in an occupational setting and reinforces previous data suggesting the effectiveness of amplification in reducing the vocal load in schoolteachers. Implications of the data for future research regarding prevention and treatment of occupational voice disorders are discussed.     

New insight into the parasitic bipolar amplification effect in single event transient production

In this paper,a new method is proposed to study the mechanism of charge collection in single event transient (SET) production in 90 nm bulk complementary metal oxide semiconductor (CMOS) technology.We find that different from the case in the pMOSFET,the parasitic bipolar amplification effect (bipolar effect) in the balanced inverter does not exist in the nMOSFET after the ion striking.The influence of the substrate process on the bipolar effect is also studied in the pMOSFET.We find that the bipolar effect can be effectively mitigated by a buried deep P+-well layer and can be removed by a buried SO 2 layer.