基于状态变量x0+Δx分解的配电自动化规划研究

在新型电力系统背景下,不确定因素的广泛接入为配电网可靠性带来了巨大挑战。为更合理地配置配电自动化终端以解决可靠性问题并提升方案的经济性,提出了基于状态变量分解的配电自动化规划模型。首先,根据相关导则和文献研究的总结,初步构建了供电单元网架规划和自动化配置映射集合;其次,以状态变量分解和局部线性化的方式将电网整体规划问题转换为供电单元局部规划问题,并在连续化后以卡罗需-库思-塔克(Karush-Kuhn-Tucker,KKT)条件求解;最后,通过对某地城市配电网的算例研究,分析了不同接线方式下终端配置数及线路分段数对投入产出比的影响,得出了不同情况下的最优配置方案,验证了所述模型的有效性。     

Dielectric Properties of Bi4−x La x Ti3O12 (0 ≤ x ≤ 2) Ceramics

The dielectric properties of the Bi_4–x La _x Ti₃O₁₂ (0 x 2) ceramics were characterized and discussed together with the P-E relation (polarization vs. electric field). With increasing x, the P-E relation changed from normal ferroelectric hysteresis loops to pure linear relation, which indicated that La³⁺ substitution for Bi³⁺ in Bi₄Ti₃O₁₂ induced a phase transition from ferroelectric to paraelectric state at ambient temperature. Low loss dielectric ceramics with temperature stable dielectric constant were obtained for x > 1.2 in Bi_4–x La _x Ti₃O₁₂ at 1 MHz. And the loss increased in all the compositions when the ceramics were measured at microwave frequencies.     

Properties of CaTi1 − x Fe x O3 − δ Ceramic Membranes

CaCO₃, TiO₂ and Fe₂O₃ were mixed in the appropriate stoichiometric quantities and calcined at 1100C for 10 h. These powder mixtures were uniaxially pressed and sintered at temperatures ranging from 1350 to 1500_C for 2 h in order to obtain dense disk-shaped samples with nominal CaTi_{1 – x}Fe_xO_3– (x = 0.05, 0.15, 0.20, 0.40 and 0.60) compositions. Dilatometry and in situ high temperature powder X-ray diffraction analysis showed a good agreement on the thermal expansion behaviour of these materials between room temperature and 1000_C. The estimated linear thermal expansion coefficient is close to 13× 10^{– 6} K^{– 1} and is little affected by composition. No evidence for surface carbonation was detected in the infrared spectra collected on samples previously annealed in CO₂ atmospheres. The oxygen permeability measured at temperatures ranging from 750 to 1000_C goes through a sharp maximum for x = 0.20. This result is interpreted by structural differences related to change from disordered to ordered oxygen vacancies. The overall performance of CaTi_0.80Fe_0.20O_3– is compared to other mixed conducting materials.     

背散射x射线缺陷检验法初探

一、前言适用于x射线透照试验的方法,在现场多是将x射线装置和检出器(x射线盒装胶片)配置于试验体的两侧。背散射x射线检验法,是将微细x射线束照射到试验体上,根据试验体后方产生的背散射x射线的强弱,来检验出存在于试验体上射线侧的近表面缺陷。     

用活Windows9x的文件管理器

在文件管理方面,如果你想在Windows 9x中寻找Windows3.x的感觉,那么请跟我来。经过以下步骤,你不但能旧梦重温,而且会感到更方便快捷。 一、在桌面上建立文件管理器的快捷图标 在桌面空闲处单击鼠标右键,在“新建”中选“快捷方式”,当出现“创建快捷方式”对话框时,在“命令行(C)”中输入“c:\windows\winfile.exe”,之后点击“下一步”,再在“为程度选定     

微型x—γ射线测量仪

介绍了一种新型ｘ－γ射线测量仪，它体积小巧，主ＣＰＵ为ＭＣ６８ＨＣ０５Ｌ５。讨论了它的硬件和软件设计。     

Dielectric relaxation and variable-range-hopping conduction in BaSn1−x Cr x O3 system

The possibility of formation of a solid solution in the system BaSn_1−x Cr _x O₃ has been explored upto x ≤ 0.20. It has been confirmed that single phase solid solution forms upto x ≤ 0.10. Dielectric and conduction behaviour of single phase samples have been studied in the temperature range 400–610 K and frequency range 10 Hz–2 MHz. Two dielectric relaxation processes in two different frequency ranges have been observed. The temperature dependence of both dc and ac resistivity obey relation ρ = ρ _o exp(B/T^1/4), indicative of variable range hopping conduction mechanism. The activation energy for dc conduction is higher than that for relaxation time (τ) of low frequency dielectric relaxation process. It has been observed that activation energy for dielectric relaxation matches with activation energy for ac conductivity (at 100 kHz) for both the dielectric relaxation processes. Seebeck coefficient ‘α’ of the samples have been measured in the temperature range 350–650 K. Negative value of ‘α’ in the entire range of temperature measurement shows that conduction species are negatively charged. On the basis of value of activation energy for dc conduction and sign of Seebeck coefficient, conduction in the low temperature region (below 500 K) is attributed to hopping of weakly bonded electrons among Sn²⁺ ⇔ Sn⁴⁺ or Sn³⁺ ⇔ Sn⁴⁺ and that in the high temperature region (above 500 K) to hopping of doubly ionized oxygen vacancies .     

Study of polycrystalline Ba1−x Ca x MoO4 films prepared by electrochemical technique

The polycrystalline Ba_1?x Ca _x MoO₄ films were prepared directly on molybdenum substrates by electrochemical technique. The growing characteristics of the films were studied by scanning electron microscopy (SEM), x-ray diffraction (XRD), and energy dispersive x-ray analysis (EDRX) techniques, respectively. The SEM images show that the morphology of the Ba_1?x Ca _x MoO₄ film is affected significantly by the composition of the films when the process parameters are preset. The XRD and EDRX analyses reveal that the compositions of the films are strongly controlled by the capability of bond between cation and anion, besides the cation concentration, temperature, and current density, in such situation.     

Structure and dielectric properties of Bi5−x La x Nb3O15 ceramics

Bi_5?x La _x Nb₃O₁₅ (x?=?0–?1.25) ceramics prepared by conventional solid-state reaction were studied using X-ray diffraction (XRD), electron probe microanalysis (EPMA) and dielectric spectroscopy techniques. The XRD analysis indicated single phase solid solution of Bi_5?x La _x Nb₃O₁₅ is formed for x?≤?1.25. EPMA showed good densification and homogeneous microstructures for the ceramics. With increasing x, the dielectric constant decreases monotonously and can vary from 258 to 158 at 300 kHz. The frequency dependence of dielectric constants indicated these ceramics are promising candidates for high frequency applications.     

求解f＇（h（x））＝g（x）的若干公式

求解ｆ＇（ｈ（ｘ））＝ｇ（ｘ）的若干公式汤光宋，周迅（江汉大学武汉４３００１０）（湖北省直属机关业余大学武汉４３００００）公式１设为非零常数，则注很明显，文［１］的定理亚～定理６＇均为公式１的特例．对公式１作进一步的推广可得公式２设ｈ（Ｘ）ＥＣ’，ｋ...     

国外最新x—y记录器技术

硬件技术主机x—y记录器要求较高的精度,它们最初是作为测试仪器来研制的。此外,由于这种仪器80%是机械的,故它的可靠性基本上是由机械零件的可靠性来决定的。因此,鉴于螺丝连接会发生松动,主机应当尽可能少用这种连接来制作。所以,现在盛行的趋势是采用压铸型造法,将主机制成一个单一的组件。伺服系统     

携带式工业x射线机简易注油法

X射线机是无损检测的重要工具之一.随着工业设备的现代化及质量要求的提高,X射线机的应用也将会更为普遍.本文简单介绍一下使用1505X射线机的一点体会.1505X射线机在电厂检修工作中使用量很大.由于工作环境较差、工作时间较长等原因,X射线机常常发生故障,如射线管不亮、油内存在气泡以及变压器油老化等等,直接影响了检测工作的正常进行.X射线机内的变压器油起两种作用——散热与绝缘,且其绝缘性随着使用时间及环境条件变化.如果变压器油的绝缘性不够,X射线机就不能正常工作.因此,维修射线机时突出的问题就是更换变压器油.更换变压器油,须采用真空注油法.在射线机     

Raman Scattering Study of the Pb(Hf x Ti1−x )O3 Ceramics

Raman spectroscopy was used to study the long wavelength vibrations of tetragonal perovskite (space group P4mm) Pb(Hf_xTi_1–x)O₃ (PHT) (0.10 x 0.50) samples at room temperature and at 20 K. For x 0.40, Raman spectra collected from the PHT samples were very similar to the previous spectra collected from the PZT samples with the same value of x, except the mode at around 190 cm^–1, whose frequency was decreasing with increasing x in PHT ceramics. Correspondingly, the latter feature was taken as a sign of the mass effect (Hf versus Zr) while the similarity of the remaining parts of the Raman spectra was assumed to be due to the almost identical ionic radii difference between Ti⁴⁺ and Zr⁴⁺ and between Ti⁴⁺ and Hf⁴⁺ ionic radii. The behaviour of the mode at around 280 cm^–1 revealed that a phase transition occurred once x was changing from 0.40 to 0.50.     

Structure and microwave dielectric properties of Sm(2−x)/3Li x TiO3

The structural evolution, and microwave dielectric properties of ceramics (x = 0.0 ≤ x ≤ 0.5) were investigated in this work. X-ray diffraction (XRD) results show that samples with x > 0.3 exhibit a single perovskite phase. Impurity phases of Sm₂Ti₂O₇ and TiO₂ appear and their amount increases with the decrease of x when x ≤ 0.3. TEM observation indicates that the A-site is ordered in x = 0.5, but not in x = 0.3). The dielectric constant decreases with the increase of x for 0.1 ≤ x ≤ 0.4 and then increases with further increase in x up to x = 0.5. The Q×f value decreases with the decrease of x due to the increased occurrence of Sm₂T₂O₇ secondary phase, defects and twinning boundaries. The temperature coefficient of resonant frequency is negative and its absolute value decreases greatly with the decrease of x value.     

802.1x 协议安全性能的改进

在宽带接入认证方案中,802.1x以其实现简单、高认证效率、高安全性正在被广泛的使用,特别是在校园网络应用非常普遍.同时用户口令失窃和口令扩散的情况非常多,由于MAC、IP 地址假冒所发生的网络安全问题也非常突出.业界普遍采用IP MAC绑定的做法,但此方案由于未能彻底防止MAC假冒,有待提高.本文分析了IEEE802.1x的体系结构,认证过程及协议报文结构.在此基础上,提出了一套解决方案.即通过专有的802.1x认证客户端在传送EAP的Response报文时,在Identity字段中携带认证端通过特殊加密处理的真实MAC.同时在Radius认证服务器端做相应解密处理,确保只有专有的认证客户端才能认证成功,从而彻底解决上述问题.     

Effect of Mg doping on dielectric properties of sol-gel derived (Pb0.7Sr0.3)Mg x Ti1–x O3–x thin film

(Pb_0.7Sr_0.3)Mg _x Ti_1–x O_3–x (x?=?0?～?0.3) thin films were successfully prepared on ITO/glass substrate by sol-gel technique. The crystalline phase structures were measured through X-ray diffraction (XRD). The dielectric properties were measured by a precision impedance analyzer. Results show that the perovskite phase was stable in (Pb_0.7Sr_0.3)Mg _x Ti_1–x O_3–x thin film. Its lattice constant was found to decrease with the increase of x when x?<?0.1 and increase when x?>?0.1.The crystalline phase formation and the dielectric properties of the (Pb_0.7Sr_0.3)Mg _x Ti_1–x O_3–x thin film depend on Mg doping content. The phase formation ability was decreased below x?=?0.1 and then increased above x?=?0.1 with the increase in x. The dielectric constant of the thin film is correspondingly changed. The tunabilities of about 35%?～?63% were obtained at 10 kHz. The highest tunability and the lowest dielectric loss of the thin films appeared at x?=?0.2. The FOM of the thin film with Mg doping of x?=?0.2 is about three times higher than that of x?=?0.1 under applied frequency of 10 kHz.     

Electrochemical evaluation of La1 − x Ca x CoO3 cathode material for zinc air batteries application

We synthesized nano-sized La_1???x Ca _x CoO₃ (x?=?0.1–0.4) cathode catalysts for zinc air secondary batteries by the citrate method, and measured electrochemical characteristics of the cathodes according to the cathode catalyst’s calcium content. We heat treated the prepared precursor at a calcination temperature of 700°C, and examined it by XRD analysis and electrochemical evaluation. We examined the prepared La_1???x Ca _x CoO₃ catalyst powder’s oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and cycle-stability performance. When we consider ORR, OER and cycle-stability performance simultaneously, La_0.9Ca_0.1MnO₃ catalyst showed the best performance because of its lowest voltage deference between charge and discharge, and its lowest degradation according to cycle.     

Microstructure dependence of microwave dielectric characteristics in Ba6-3x Sm8+2x Ti18O54 (x = 2/3) ceramics

Effects of microstructures on the microwave dielectric characteristics of Ba_6-3x Sm_8+2x Ti₁₈O₅₄ (x?=?2/3) ceramics were investigated by controlling the sintering process and the annealing condition. The dielectric constant was sensitive to the porosity in ceramics, but insensitive to the annealing process. Q f value varied with both the annealing atmosphere and the sintering temperature, which indicates the strong reliance of dielectric loss on defects and grain boundaries. τ _f value exhibited a complex dependence on the sintering temperature. The orientation of grains is responsible for the variation of τ _f .     

Low-temperature sintering and dielectric properties of the Bi(Nb1−x Ta x )O4 system

Low-temperature sintering and dielectric properties of the Bi(Nb_1?x Ta _x )O₄ (x?=?0.1, 0.3, and 0.5) system was investigated as a function of the zinc borosilicate (ZBS) glass content with a view to applying this system to LTCC technology. The addition of 7 wt% ZBS glass ensured a successful sintering below 900°C. The complete solid solution of Bi(Nb, Ta)O₄ with an orthorhombic structure was formed and the high temperature form of Bi(Nb, Ta)O₄ with a triclinic structure was not observed. The second phase of Bi₂SiO₅ was observed for all compositions. The non-relative liquid phase sintering (NLPS) occurred and the one-stage sintering was conducted. The Q?×?f values were improved by the addition of Ta. Bi(Nb_0.7Ta_0.3)O₄ with 7 wt% ZBS glass sintered at 900°C demonstrated 35.8 in the dielectric constant (? _r), 2,200 GHz in the quality factor (Q?×?f ₀), and ?48 ppm/°C in the temperature coefficient of resonant frequency (τ _f).     

用于x射线探伤的新曝光图

引言新曝光图除了能给出获得一定黑度的底片所需的曝光条件外,还能同时得到透度计灵敏度这一重要参数。本文通过对新曝光图的介绍,综述了国外近些年来在X射线探伤技术中所采用的一些新概念和实验结果。这不仅是制作新曝光图所需要的,而且在定量地研究X射线照相的许多其他问题时,都要涉及到。