Co掺杂ZnO块材的晶体结构和磁性能研究

采用固相法制备了Zn1-xCoxO（x=0．05-0．25）块材,烧结温度和Co含量对Zn1-xCoxO（x=0．05-0．25）块材的晶体结构和室温磁性能影响强烈,当x≤0．1,烧结温度从800增加到1100℃时,Zn1-xCoxO（x=0．05-0．25）呈现出单相结构,但当x〉0．1,烧结温度为800℃时,样品中出现CoO相;随着烧结温度提高到900℃,样品再次获得纯的单相结构。为了获得高的饱和磁化强度Ms,最佳烧结温度应该根据Co含量进行调整。在最佳烧结温度条件下,当x从0．05提高到0．1时,Ms从0．79增加到了1．06μB/Co,但当x继续提高到0．2和0．25时,Ms分别降低到了0．59和0．41μB/Co。     

新型稀土镁基贮氢电极合金的结构与性能

系统研究了La0．7Mg0．3(Ni0．85Co0.15)x(x=2．5，3．0，3．5，4．0，4．5，5．0)贮氢电极合金的结构和储氢性能．该类型合金由(La，Mg)Ni3相(PuNi3型结构)和LaNi5相(CaCu5型结构)组成，两相的a轴参数和晶胞体积都随着x值的增大而减小．(La，Mg)Ni3相的丰度先从x=2．5时的48．4％增加到x=3．5时的78．2％，然后又减小到x=5．0时的12．2％，而LaNi5相的丰度在x=2．5-3．5时基本保持不变(-20％)，在x=4．0时突然增加到71.9％．合金的吸氢量从x=2．5时的0．86％(质量分数)增加到x=3．5时的1．50％然后又减小到x=5．0时的1．19％．合金的放氢平台压力在x=2．5-3．5时保持基本不变(-65．9kPa)，然后逐渐增加到x=5．0时的0．30MPa．随着x的增加，吸放氢过程的滞后效应先增大后减小，而合金的放氢平台变得更加平坦．     

填充聚合物分解热效应对锥形量热法测热结果的影响

研究了应用锥形量热仪测量填充聚合物复合材料燃烧的热释放速率时。填料的分解热效应对测量结果的影响．结果表明,若不对锥形量热仪所测得的结果进行校正,则对强分解吸热的填料,测量结果偏高．定量研究表明,对氢氧化铝和氢氧化镁填料,当氢氧化铝填料的质量分率为80％时．基于PP、PM．MA和PVC的复合材料的燃烧热分别减少了11．1％、19．3％和29．2％;当氢氧化镁填料的质量分率达到80％时。基于PP、PMMA和PVC的复合材料的燃烧热分别减少了13．2％、22．9％和34．7％．在此情况下．测量结果存在很大误差．并且其具体值还因聚合物而异．文中在定量研究的基础上．提出了一种利用分解焓对锥形量热仪测定的有效燃烧热值进行校正的方法。并给出了校正后的结果同原实验值的比较。     

参数扰动的RLC低通滤波器的随机共振

研究了RLC低通滤波器在电导受到非对称双值色噪声扰动时的随机共振现象．利用随机平均法和Shapiro—Loginov公式,得到了平均输出幅度增益的精确表达式．分析表明,在欠阻尼、临界阻尼和过阻尼RLC低通滤波器中,平均输出幅度增益对电导噪声的非对称性、相关时间、强度和信号频率都存在非单调依赖关系．适当的噪声和系统参数条件可以使有噪声时系统的平均输出幅度增益大于没有噪声时系统的平均输出幅度增益．噪声可以提高滤波器对高频信号的衰减率．恰当的条件可以获得平均输出幅度增益的最大值．     

运动刚体激励下弹性梁的振动响应分析

本文研究了与弹性梁有两点接触的运动刚体对梁激励时的响应，以悬臂梁为例进行了数值计算及实验研究．发现运动质量在梁上运动时，梁呈非周期振动；而且，最先产生响应的位置大约在梁的中部，而不是在质量作用点或梁端部．实验验证了计算结果．     

薄膜厚度对多层膜巨磁阻抗效应的影响研究

采用磁控溅射方法在玻璃基片上制备了FeSiB／Cu／FeSiB多层膜,在100kHz～40MHz范围内研究了FeSiB薄膜厚度对FeSiB／Cu／FeSiB多层膜巨磁阻抗效应的影响。当磁场施加在薄膜的纵向时,巨磁阻抗效应随磁场的增加而增加,在某一磁场下达到最大值,然后随磁场的增加而下降到负的巨磁阻抗效应。当FeSiB薄膜的厚度为1．8μm时,在频率3．2MHz、磁场2．4kA／m时,多层膜巨磁阻抗效应达最大值13．5％;在磁场为9．6kA／m时,巨磁阻抗效应为-9．2％。然而,当FeSiB薄膜的厚度为1μm时,多层膜的巨磁阻抗效应在频率40MHz、磁场1．6kA／m时达最大值5．8％。另外,当磁场施加在薄膜的横向时,薄膜表现出负的巨磁阻抗效应。对于膜厚为1．8μm的FeSiB薄膜,在频率5．2MHz、磁场9．6kA／m时,巨磁阻抗效应为-12％。可见巨磁阻抗效应的最大值及负的巨磁阻抗效应与多层膜中磁各向异性轴的取向及FeSiB薄膜的厚度有关。     

工作温区为1.4至10K的卡诺磁制冷机

一台直接从１０Ｋ降温至１．４Ｋ的磁制冷机业已制成功并进行了试验。该制冷机是一种采用脉动磁体和热电开关，按卡诺循环运转的静态装置。其典型试验结果如下：采用Ｄｙ３Ａｌ５Ｏ１２制冷工质时在４．５ＫＴ制冷量为５５０ｍＷ；在１．８ＫＴ为１００ｍＷ；无冷负荷时，获得的最低温度为１．３６Ｋ，２．０Ｋ时的卡诺效率为３０％；４．４Ｋ时为３８％。另外还完成了有关磁体的一些试验。     

扬眉出鞘剑指何方——兴安集团（福建）有限公司的品牌之路

秣马砺剑正逢时．搏击市场竞风流。在新经济时代的今天．市场经济日益全球化．中国经济融入世界经济大潮中．给兴安集团有限公司带来机遇也带来了挑战。     

具有吸毒年龄和治疗年龄的海洛因模型的全局稳定性（英）

本文建立了一个吸毒人群具有吸毒年龄,治疗人群具有治疗年龄的海洛因传播模型．得到了基本再生数．通过波动引理和李雅普诺夫泛函,证明了当基本再生数小于1时无海洛因吸食平衡点是全局渐近稳定的,当基本再生数大于1时,海洛因传播平衡点是全局渐近稳定的．     

高韧性药芯焊丝焊缝金属的显微组织

测试了高韧性药芯焊丝焊缝金属在－２０℃时的ＣＴＯＤ阻力曲线,用扫描电镜和透射电镜分析了焊缝金属的显微组织,测定了焊缝金属中非金属夹杂物尺寸大小。结果表明,焊缝金属含有约９０％的针状铁素体时,在－２０℃时的断裂韧性特征值δ０．２可达０．１５１ｍｍ。     

Noise properties of a quadrature phase tracker for interferometricoptical fiber sensors

The noise performance of an electronic quadrature phase-detection system for interferometric optical fiber sensors is presented. Three noise sources are discussed in this work, namely, synchronous detection-circuit noise, phase-perturbation noise; and additive amplitude noise. We determined the output signal-to-noise ratio (SNR) experimentally as a function of input phase power for each of the three noise sources. For uncorrelated synchronous detection-circuit noise the output SNR increases monotonically with input phase power. For correlated noise the output SNR has distinct peaks due to noise cancellation. System performance is limited by uncorrelated detection-circuit noise which exhibits a threshold behavior in output SNR at a phase shift of 25 mrad/Hz^½. The phase noise has a more conventional behavior in the sense that SNR gain occurs only at the expense of dynamic performance. Uncorrelated amplitude noise also displays noise cancellation at certain discrete values of input phase, as is the case for correlated synchronous detection-circuit noise. System insensitivity to correlated light-source amplitude noise is evident from the fact that the output SNR is more than 30 dB higher than the input SNR     

Impossibility of Linear Two-Port Noise-Parameter Measurement with a Single Temperature Noise Source

The noise parameters of a linear two-port are usually evaluated through four measurements of the noise figure of the two-port, and the noise figure is in turn determined through the measurements of the noise power output of the two-port when a noise source is connected at its input. It is shown that if the noise power output is the only measured quantity, then the noise parameters cannot be calculated from measurements carried out with a single value of the source noise temperature. The minimum requirements for the determination of noise parameters are established.     

船台生产作业噪声治理及声屏障降噪效果预测

针对造船厂船台生产作业噪声治理及降噪效果预测难的问题,提出船台噪声的治理方法。以某造船厂船台噪声治理为例,结合某造船厂船台噪声治理实例,提出船台噪声的治理方法,并针对其噪声特点,对噪声源进行建模,预测了主要治理措施的降噪效果。结果表明,造船厂船台生产作业噪声需从声源、声传播途径及生产作业管理等多方面进行综合治理;除降噪效果外,声屏障的设置还需考虑施工可行性、社会因素以及经济性等实际情况;对于船台生产作业噪声等分布范围广、密度大、垂向位置高的声源的模拟预测,需根据声源实际工况进行针对性建模。研究可为船台生产作业噪声等类似噪声源的噪声治理和预测提供参考。     

Noise of piezoelectric accelerometer with integral FET amplifier

Since significant progress has been achieved in the development of low-noise piezoelectric (PE) accelerometers with integral FET amplifiers, detailed noise analysis of the system PE transducer-FET amplifier, and obtaining the engineering formula for its noise floor has become vital. As a result of this analysis, the formula for the noise floor of PE accelerometers in terms of acceleration spectral density is obtained at wide frequency band. Noise floor of the low-noise PE accelerometer comprising low-noise JFET charge amplifiers with some particular parameters of the PE transducer and the JFET amplifier was measured. The theoretical and experimental curves of the PE accelerometer's noise floor have a good correlation with each other at frequencies from 1 Hz to 10 kHz. The contribution of the different noise sources to the overall noise floor is shown. Those noise sources include the mechanical-thermal noise and electrical-thermal noise of the PE transducer and all main noise sources of FET amplifiers: the thermal noise voltage of the FET biasing resistor, the thermal noise of the series resistor between the PE transducer and the gate of the FET, the channel thermal noise voltage, the 1/f noise voltage, and the shot noise current in the gate circuit. At low frequencies, the f/spl les/50 Hz noise floor is determined mainly by the FET biasing resistor's thermal noise and the PE transducer's electrical-thermal noise. At frequencies from about 50 Hz to about 1 kHz, the contribution of the PE transducer's electrical-thermal noise dominates over the amplifier's noise sources by a factor of less than 2. At frequencies above 1 kHz, noise floor is determined mainly by the JFET channel thermal noise and the PE transducer's electrical-thermal noise.     

Phase noise performance of microwave analog frequency dividers: application to the characterization of oscillators up to the millimeter-wave range

The phase noise performance of two different microwave analog frequency dividers is characterized and compared with the values obtained using simple theories of noise in injection-locked systems. The direct measurement of the divider noise with a low phase noise synthesizer is not accurate enough, and the residual noise technique is used. The noise levels observed using this technique, between -120 and -155 dBc/Hz at a 10 kHz offset frequency, demonstrate that this divider noise is much lower than the phase noise of most microwave free running oscillators, even if this noise is still high with respect to the residual noise of amplifiers realized with the same active devices. The down conversion of microwave sources up to 40 GHz, is proposed as an application example.     

牵引电机传动系统噪声及振动分析

通过牵引电机传动系统噪声及振动的特性分析,采用噪声与振动分析系统对牵引电机传动系统进行噪声与振动测试,分析得出：随着转速的提高噪声值增加,并主要分布在频率为800 Hz附近,MIC02噪声高于MIC01噪声;齿轮箱的振动要高于电机振动。其研究结果对牵引电机传动系统减振和降噪设计提供依据。     

带阻塞喷射的大流量排气管降噪处理

针对高温高压燃烧实验间中的排气噪声,在前期降噪尝试和频谱测量确定了噪声源基础上,设计了由多孔共振腔和多孔排气管组合的消声器,消除由临界孔板产生的刺耳的高频阻塞噪声,降低噪声总声压级。经实验测定,噪声的折合声压级降低了21 dB,取得明显降噪效果。不同消声器的组合为实验室的排气降噪提供了参考。     

高速铁路噪声预测方法及其在昌九城际轨道交通中的应用

在对城市轨道交通的噪声源特点进行分析的基础上,介绍噪声预测方法,并与国外的成熟方法进行对比分析;重点介绍把城市轨道交通噪声作为一个线声源、噪声源分解为轮轨噪声和牵引噪声等分别进行预测的方法,并给出了详细的计算步骤。以此方法对昌九城际轨道交通的噪声水平进行预测,得到沿线敏感点在昌九城际轨道交通影响下的环境噪声级。     

电视台风机及风机房减振降噪治理

噪声与振动本上消除振动和噪声.本文通过对电视台转播设备噪声与振动源分析,制定出合理的噪声与振动控制方案,从而有效地解决了噪声与振动问题.