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一般的工频磁场测量仪在静止状态下测量,针对移动情况下工频磁场的测量问题,研究了一种工频磁场动态测量方法。由该方法设计实现的工频磁场测量仪与EMDEXMATE个体磁场暴露计的比较试验表明,该方法可以动态测量磁场,测量误差稳定在10%以内,也可根据需要用于动态测量工频磁场水平方向和竖直方向上的分量。本文根据磁场测量分解原理,针对行进过程中非重力因素对获取重力分量的影响,将磁场测量和三轴磁场传感器的姿态相结合,探索一种可以进行动态测量的工频磁场测量仪的设计方案。 相似文献
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研究了电子在有同向磁场的平面摆动器中的自发辐射和谐波相干辐射,得到了一个较普遍的自发辐射谱表达式和谐波自由电子激光的增益。当电子的能量较高或者沿摆动器轴线观察时,辐射是椭圆极化的,适当附加轴向磁场,可以提高激光增益,对于较低次谐波,增益提高更明显。 相似文献
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本文介绍一种基于单片机的工频弱磁测量系统,能测量一毫高到一千毫高范围内、方向未知的工频磁场,可以作为环境工频磁场的有效监测手段. 相似文献
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介绍电磁兼容抗扰度试验中,常用的工频磁场感应线圈及工频磁场发生器的基本原理和相应的校准方法,并对校准结果和校准过程中遇到的问题进行了详细分析. 相似文献
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本文对二维摆动磁场自由电子激光的自发辐射频谱进行了理论分析,并对分析结果进行了数值计算。计算结果表明,采用l(lk2=ky)值不同的二维摆动磁场,可以增强第l次谐波的自发辐射强度,从而能够有选择地实现自由电子激光的高次谐波运转。 相似文献
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《Microelectronics Journal》2003,34(5-8):623-625
The electroluminescence from PPV and the blue light emission from PPP constitute exciting subjects of study. The band gap of these semiconducting polymers can be engineered in a wide range from red to ultraviolet by structural changes made on them. In the present work, we present a theoretical approach based on semiempirical and ab initio total energy and force calculations of PPV and PPP. We perform a conformational analysis in order to investigate the connection between their structural, optical and electronic properties. We use the large cell approach, in connection with the semiempirical quantum method Extended Hückel (BICON-CEDiT code) and the density functional theory (DFT) within the full-potential linearized augmented-plane-wave method (FPLAPW) as implemented in the computational code WIEN2k. Our results are compared to other calculations and to optical absorption measurements. 相似文献
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通过Ta掺杂改性钨青铜陶瓷(Sr0.5Ba0.5)1.9Ca0.1NaNb5–xTaxO15(x=0~0.30),分析了Ta掺杂量对其烧结性能、微观结构及介电性能的影响。陶瓷的烧结温度随x的增大略有提高。当x<0.10时,陶瓷的tC和弛豫性变化不大;当x≥0.10时,tm(1kHz)明显降低,从270℃(x=0)降低至231℃(x=0.30)。且tm随频率增加向高温移动,弛豫性明显增强。认为Ta掺杂引起其性能变化是由于Ta—O键与Nb—O键键能的差异,导致陶瓷氧八面体中心离子位移量以及A位离子有序程度的变化所致。 相似文献
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采用熔体快淬法制备了纳米复合(Nd1-xPrx)9.4Fe75.6Ti4B10.5C0.5(x为0,0.2,0.4,0.6,0.8和1.0)合金薄带,研究了Pr对合金薄带结构与磁性能的影响规律。结果表明:Pr降低了合金薄带的晶化温度,使合金薄带晶粒变得粗大,不利于合金矫顽力的提高。Pr对合金薄带磁性能的影响不大,不同Nd和Pr比例的合金薄带在最佳热处理条件下,剩磁Br在0.86 T与0.90 T之间,内禀矫顽力Hcj在1 000 kA/m左右,最大磁能积(BH)max介于130 kJ/m3与136 kJ/m3之间。 相似文献
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Semiconductors - Electron states in the conduction band of (111)-oriented (AlAs)M(GaAs)N superlattices (SLs) with M≥N and N&;lt;10 are considered. The properties of such SLs are mainly... 相似文献
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徐至中 《固体电子学研究与进展》1989,(4)
The DOS, JDOS and ε2(Ω) of monolayer superlattice Ga0.47ln0.53As/ InP(110) have been calculated by a tight-binding approach and compared with that of alloy Ga0.235ln0.765P0.5As0.5 which has the same stoi-chiometric composition as the monolayer superlattice. By using the techniques of the group theory we have obtained the expressions of momentum matrix elements between valence band states and conduction band states with four adjustable parameters. These parameters are determined by fitting the calculated values of ε2(Ω) with the experimental values for InP, GaAs and InAs. Our results show that the superlattice periodicity makes its DOS, JDOS and ε2(Ω) different from those of alloy in varying degree. Due to the folding of Brillouin zone, the JDOS of superlattice turns round in comparison with that of alloy. The momentum matrix elements have different effects for the superlattices and alloys.For the alloys, they can only change the amplitudes of peaks but not the positions of peaks; however, for the superlattices both amplitude and position can be changed. 相似文献
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The deformation potentials of electron scattering at short-wavelength phonons for intervalley transitions in the conduction band of short-period (GaAs) m (AlAs) n (001) (m, n = 1, 2, 3) superlattices are determined by the electron density functional method. The dependences of the electron and phonon states and deformation potentials on the layer thickness in the superlattices are analyzed. The results of ab initio calculations are in good agreement with the data of empirical calculation of the deformation potentials integrated over phonons, but differ from data on the corresponding potentials for partial scattering channels because of approximations of the phenomenological model of interatomic binding. 相似文献
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采用两步烧结工艺制备Sr0.3Ba0.7Bi3.7La0.3Ti4O15铁电陶瓷,研究了烧结工艺对陶瓷的晶相和介电性能的影响。结果表明:适当提高最高温度、保温温度和保温时间可改善陶瓷的介电性能。当最高温度为1180~1200℃,在1050~1080℃保温5~15h时,其εr为238~262,tanδ小于10–2,σ为1.0×10–11~10–12S·m–1。该烧结工艺可减少铋的挥发,降低氧空位浓度,因而减弱了陶瓷的高温低频耗散现象。随着保温时间的增加,高温电导得到有效抑制,在1050℃保温15h样品的σ降低了一个数量级,在280℃时为5.2×10–9S·m–1。 相似文献
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徐至中 《固体电子学研究与进展》1998,(4)
采用建立在经验赝历势基础上的推广k·P方法计算了复合量子阱Ge0.3Si0.7/(Ge0.3Si0.7)m-(Si)m/Ge0.3Si0.7的电子束缚能组及其活界面方向的色激关系,并与通常的单带模型下的包络函数方法的计算结果进行了比较。结果表明由于超晶格中子能带的形成,邻近能带间的互作用使通常单带模型下的包络函数方法不再能适用于复合量子阱的计算。计算结果也表明复合量子阱的电子束缚能级沿界面方向在kx<0.1(2π/a)范围内基本上不随kx变化。 相似文献