瓦特表使用中的几个问题

本文分析瓦特表两种接线方式对测量结果的影响，讨论了二表法测量三相三线制电路时，功率在两瓦特表间的分配，提出三表组合在电路测试中的应用。     

瓦特表使用中的几个问题

本文分析瓦特表两种接线方式对测量结果的影响，讨论二表法测量三相三线制电路时，功率在两瓦特表间的分配，提出三表组合在电路测试中的应用。     

在DDS中波形存储表设计的实现方法

基于FPGA器件的DDS设计实现中的一个核心部分就是波形存储表的设计.首先采用LPM_ROM和VHDL选择语句这两种方法进行波形存储表的设计和比较分析;然后考虑到硬件资源的有限性及DDS的精度要求,对这两种方法的程序进行了优化;最后对这两种方法设计的程序进行仿真和硬件调试.结果表明:采用这两种方法都能有效地实现DDS中波形存储表的设计.     

电力营业中的抄表安全管理

供电企业参与到市场竞争当中,抄表工作成为了为企业创收的一个环节。电能用户都安装电能计量表计,抄表人员采用各种抄表方式抄录电能用户所耗费的电量,以此作为收取电费的依据。在日常的抄表工作中,主要是采用人工抄表或者掌上机抄表两种方式。一些大型的供电单位引进了自动抄表技术,实现了远程抄表。随着电力需求市场的快速发展,各种抄表手段都出现了不同层次的质量问题,强化抄表安全管理成为了一种必然。     

在集中抄表系统管理中计量部门的作用

集中抄表系统实现了家用水、电、煤气表的远程抄表功能．它以保护用户隐私、避免人为抄表差错、减员增效、对历史数据集中处理管理等优点得到了开发商、用户、水电气供表企业的青睐。正越来越多地应用到新建的智能化小区。无论哪一种形式的集中抄表方式，最终都是以实现不再入户抄表．以远程抄表方式进行结算为目的的。     

浅谈VU表与PPM表在直播室的应用

音量表是电台节目监测的专用仪表,它的技术性能与质量好坏,都会直接影响播出质量。目前使用最广的音量表是VU表和PPM表。 VU表的特点 目前直播室使用最广的一种音量表是“音量单位表”,又称VU表(是英文Volume Unit的缩写)。它是采用平均值检波器(二极管桥式整流器)并按简谐信号的有效值确定的,因此是一种准平均值表。     

新技术的推广应用RFID射频抄表机

主要阐述广州市自来水公司改变传统的抄表模式,采用RFID抄表机代替手工帐册进行抄表并推广应用,并简要阐述RFID抄表机的组成、工作原理、功能及使用意义.     

使用内径表测量时应注意的问题

作为一名计量人员 ,在车间巡查时 ,经常会发现一些工人和工程技术人员 ,随意更换内径表的指示表进行测量。有时将调试机床用的指示表用来作为内径表的指示表 ,有时把这只内径表的指示表与那只的混用。他们认为都是经过计量部门检定合格的 ,当然就可以这样更换使用。其实 ,这种做法是错误的。内径表的示值误差主要是由两个部分带来的 :一个是指示表部分 ,另一个是表架传动部分。经过计量部门检定合格的内径表 ,是说明其整个传动和指示系统的综合误差是在检定规程规定的允许范围内的。如果在使用时任意更换指示表 ,并没有经过计量部门的调整和…     

检定弹簧管式一般压力表,压力真空表及真空表示值方法的探讨

检定压力表一般都是采用直接比较法,即将精密压力表与被检压力表进行比较。在考核了港务局内的十几个单位的计量标准之后,我们发现在检定弹簧管式一般压力表、压力真空表及真空表(以下简称压力表)示值时有两种方法。 1.在压力表标有数字的分度线进行示值检定(包括零值)时,逐渐升压(或疏空),在压力到达相对于被检压力表某一数字,精密压力表所指示的值时,读取被检压力表的读数,逐一记录,然后     

两表测三相电功率的等效接线法

本文阐述了两表法应用于三相电功率测量的等效原理,并分析了应用该原理的几种等效接线法.     

Photostriction of CH3NH3PbBr3 Perovskite Crystals

Organic–inorganic hybrid perovskite materials exhibit a variety of physical properties. Pronounced coupling between phonon, organic cations, and the inorganic framework suggest that these materials exhibit strong light–matter interactions. The photoinduced strain of CH₃NH₃PbBr₃ is investigated using high‐resolution and contactless in situ Raman spectroscopy. Under illumination, the material exhibits large blue shifts in its Raman spectra that indicate significant structural deformations (i.e., photostriction). From these shifts, the photostrictive coefficient of CH₃NH₃PbBr₃ is calculated as 2.08 × 10^?8 m² W^?1 at room temperature under visible light illumination. The significant photostriction of CH₃NH₃PbBr₃ is attributed to a combination of the photovoltaic effect and translational symmetry loss of the molecular configuration via strong translation–rotation coupling. Unlike CH₃NH₃PbI₃, it is noted that the photostriction of CH₃NH₃PbBr₃ is extremely stable, demonstrating no signs of optical decay for at least 30 d. These results suggest the potential of CH₃NH₃PbBr₃ for applications in next‐generation optical micro‐electromechanical devices.     

Constitution of the Ni3Cr-Ni3Al-Ni3W system

Isothermal sections of the Ni-Cr-Al-W system have been investigated at 75 at % Ni and temperatures of 1523 and 1273 K, by means of phase compositional analysis, X-ray diffraction and microscopical examination. The alloys studied lay in the range 2.5 to 10 at % Cr, 12.5 to 20 at% Al, 2.5 to 6.25 at % W, The phases formed were, and the bcc solid solution based on tungsten (designated ₂). The maximum extent of the region was found to be 3 at % each of chromium and tungsten. Preferential partitioning of tungsten to occurred. Study of an Ni-10Cr-12.5Al-2.5W alloy aged at 1273 and 1073 K, after quenching from 1573 K, showed that changes in and compositions and lattice parameters occur as a function of ageing time.     

(La2/3Ca1/3)(Mn(3-x)/3)Fex/3)O3体系磁电阻行为的研究

通过系统地测量（La_2/3Ca_1/3）（Mn_{（3-x）／3}Fe_x／3）O₃（x＝0、0.1、0．2、0．3的体系样品的电阻率-温度关系以及一定温度下磁电阻率与磁场的关系,发现随x的变化其磁电阻率峰和电阻率峰均发生位移,磁电阻率峰值增大,并伴生磁电阻率峰展宽效应．作者认为由于Fe的替代,引起体系中Mn³⁺／Mn⁴⁺比率及磁矩的变化,加之外场对磁有序结构的调制作用,从而影响了Mn³⁺－O^－Mn⁴⁺的双交换作用,最终导致磁电阻行为发生变化．     

PbZrO3-CdTiO3 solid solutions

The structural, nonlinear optical, and dielectric properties of (1-x)PbZrO₃ ·xtCdTiO₃ solid solutions were studied. The phase relations in the composition rangesx = 0–0.3 and 0.85-1.0 were established. The results suggest that the ferrielectric ordering in CdTiO₃ persists up to 730 K.     

Phase equilibria in the system LaMnO3 + δ-SrMnO3-LaFeO3-SrFeO3 − d

We have revealed the formation of a continuous series of orthorhombic LaMn_{1 ? y} Fe_yO₃ solid solutions (0<y<1); La_{1 ? x} Sr_xFeO₃ solid solutions in the composition range 0 < x ≤ 0.8, with an orthorhombic structure at 0 < x ≤ 0.6 and a cubic structure at 0.6 < x ≤ 0.8; and a tetragonal SrMn_{1 ? y} Fe_yO₃ phase in the range 0.6 ≤ y ≤ 1. The composition stability limits of the perovskite phase La_{1 ? x} Sr_xMn_{1 ? y} Fe_yO₃ have been determined, and the 1100°C isotherm of the La₂O₃-SrO-Mn₃O₄-Fe₂O₃ system in air has been constructed.     

Multicolor up-conversion emissions of Tm3+/Er3+/Yb3+ tri-doped YF3 phosphors

Tm3+/Er3+/Yb3+ tri-doped yttrium fluoride (YF3) phosphors were prepared by a facile hydrothermal method. X-ray topographic analysis found that the phosphors were crystallized products. Their sizes and morphologies were characterized by scanning electron microscopy (SEM, Hitachi S-4800), which indicated that most of the YF3 phosphors were hundreds of nanometers in size. Up-conversion (UC) spectra were recorded under 980-nm diode laser excitation at room temperature with a fluorescence spectrometer (Hitachi F-4500). Plenty of UC emissions of Tm3+ and Er3+ were observed from ultraviolet to red. For Tm3+ ions, a five-photon process (approximately 291 nm and approximately 347 nm), a four-photon process (approximately 362 nm and approximately 452 nm), and a three-photon process (approximately 475 nm) were identified in the UC spectra. The UC emissions from the Er3+ were: approximately 380 nm, approximately 408 nm, approximately 521 nm, approximately 537 nm, and approximately 652 nm. Therefore, cyan-white light can be observed by the naked eye at 980-nm excitation, even under low excitation power density. By comparing the UC spectra of the phosphors annealed at different temperatures, we found that the intensity of the UC luminescence increased as annealing temperature increased. Furthermore, the spectral dependencies on Tm3+ doped concentrations were studied. The energy transfer processes and fluorescence dynamics in the tri-doped system are currently being investigated.     

3 Cr3 Mo3 VNb 在热冲孔中的应用研究

高合金钢热冲孔冲头寿命关系到模具与产品成本、生产效率、自动化设备的使用,因此,应注重冲头的选材、材料制备与冲头制造工艺。 用 3 Cr3Mo3 VNb 作为高合金钢热冲孔冲头,为提高模具寿命,在材料制备上,优化了成分,采用电渣重熔冶炼,减少杂质,毛坯锻造两次,用大锻造比锻造,冲头热处理用真空炉,三次回火,热处理硬度取 HRC42 ~ 46 ,冲头表面处理采用镀铬工艺,开展了热冲孔工艺试验。 结果表明,用3 Cr3Mo3 VNb 可使冲孔冲头寿命平均达到 800 件以上。     

Processing and properties of Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3 ceramic relaxors

The shrinkage phenomenon during the reaction-sintering of PMN-PZT from low-temperature pre-reacted 3PbO + MgNb₂O₆ + PZT powder mixtures has been studied. It was assumed that the pre-reaction treatment leads to the formation of a pyrochlore phase containing very active MgO small particles, and that the strong shrinkage occurring up to 800 °C took place by the diffusion of Mg²⁺ cations into the pyrochlore phase particles, thus controlling the reaction-sintering shrinkage phenomenon. Above that temperature the densification was enhanced by a liquid-phase sintering process. The ceramics sintered at 1050 °C for 2 h showed 96% of the theoretical density, and the dielectric constant of such a sintered ceramic showed a maximum value of 17 000 at 1 kHz. It was also found that the dielectric constant decreased with increasing grain size. Although the role of PZT in enhancing the dielectric constant of otherwise low-purity PMN ceramics is not clear, the increase in K is assumed to be a solid-solution effect. The presence of impurities and the PbO stoichiometry could be influencing the not too high dielectric constant value of PMN-PZT ceramics.