Modeling and Analysis of a Long Thin Conducting Stripline

A long thin conducting stripline embedded in a dielectric and centered between two large conducting plates, i.e., the stripline environment, is considered. The stripline is modeled as infinitely long, infinitely thin, and perfectly conducting by first considering a stripline of finite length, thickness, and conductivity in a dielectric layer. Starting from Maxwell's equations and assuming that the current on the stripline is a propagating wave in length direction, asymptotic expressions for the fields inside and in the neighbourhood of the stripline are deduced. These expressions are used to model the stripline in the stripline environment, which leads to a boundary-value problem for the electric potential. This problem is solved by two different approaches, leading to integral equations for the current and for an auxiliary function describing the electric potential. A relation between the current and the auxiliary function is deduced, which is used to obtain asymptotic expressions for current and impedance. Results are compared with a numerical solution of the integral equation for the current and with results in literature.     

一种考虑分布电容的模糊故障测距算法

提出了一种考虑分布电容的故障测距新算法。该算法基于微分方程描述的线路数学模型，利用单端信息对高压输电线路进行故障测距，保留了解微分方程算法的简单可靠、现实可行、不必考虑衰减直流分量和谐波及电网频率波动影响的特点，同时考虑过渡电阻和分布电容的影响，克服了传统解微分方程法中在经高阻接地故障时测距误差过大和忽略分布电容引起的故障定位不准确的缺点。为了检验算法的精度，进行了大量的动模实验。结果表明，算法原理正确并具有较高的测距精度。     

Breakdown of oil films and formation of residual films

The breakdown processes of oil films under quasi-static loading have been investigated by using a newly developed steel-oil-mercury system. The relationship between the thickness and breakdown ratio of a hexadecane film is represented by a single master curve independently of the indentation speed, indentation load, and temperature. The master curve shows that the breakdown process of hexadecane includes two stages; one is the decrement of the thickness without breakdown and the other is the decrement of the thickness with a drastic progress of breakdown. By solving a small amount of fatty acid in hexadecane, the thickness increases and the breakdown ratio decreases noticeably; a multilayer residual film supporting normal load is formed between two metal surfaces. Experiments at different temperatures reveal a negative relationship between the temperature and thickness of residual film, which indicates that the residual film is organized by physical interaction rather than chemical interaction. At least under a lower concentration, the residual film appears to consist of not only fatty acid molecules but also hexadecane molecules.     

弱电系统中的地线干扰与接地方法

介绍了地线的干扰机理以及减小地线干扰的对策和接地的基本方法.在电子电路中,地线不仅为电路提供一个电位公共参考点,而且也为电流提供一条能够流回源的低阻抗路径.由于地线存在阻抗,当电流流过地线时,会在地线上产生电压差,从而形成地线干扰,严重时将会影响电路的正常工作.减小或消除地线干扰的主要方法是减小地线的阻抗和地线电流.为此,可以针对不同的信号频率及干扰性质,根据系统的结构和功能采用相应的接地方式,将接地、屏蔽及滤波等措施结合使用.     

Comparison of activities in selective catalytic reduction of NOx by C3H8 over Co/MFI, Fe/MFI, and H/MFI zeolite catalysts

The Co/MFI(SiO₂/Al₂O₃ = 30) were prepared by a precipitation method with NaOCl in alkali solutions exhibited high activities to N₂ at 250 °C for the selective catalytic reduction (SCR) of NO_x. These catalysts showed two UV–vis bands at 700 and 400 nm, indicating the presence of octahedral Co(III) as well as tetrahedral Co(II). The high SCR activity over such Co(III, II)/MFI(30) seems to come from Co(III)---O moieties. The Co(II)MFI(30) catalysts prepared from Co(II)Cl₂ exhibited low SCR activities due to the presence of tetrahedral Co(II) ions in MFI. Less CO formation occurred over Co/MFI catalysts. The Fe/MFI(30) catalyst exhibited high activity due to the presence of some Fe---O species in MFI but more amount of CO were produced during SCR. H/MFI(30) catalyst exhibited a good SCR activity. However, more amount of carbonaceous deposits were produced on it. The correlation between acid concentration and SCR activity was discussed over H/MFIs.     

Synthesis and characterisation of carboxylic acid and diphenylphosphine derivatives in the 1,3-diyne series: Spectral properties of polydiacetylene carboxylates

Symmetrically substituted 1,3-diynes containing hydroxyalkyl ( 1a-d ), bromoalkyl ( 1e-h ) (diphenylphosphinyl) ( 1i-k ) and carboxyalkyl ( 2a-d ) substituents have been prepared and characterised; the phosphine derivative ( 1k ) has been converted with alkyl iodides ( RI ; R = Me, Et) into bis(phosphonium) salts ( 1l and m ). During preparation of the diynedioic acid. ( 2a ), the non-centrosymmetrical diyne, HO₂CCH₂C?C—C?C(CH₂)₂OH ( 3 ), was also isolated. ⁶⁰Co γ-Irradiation of diacetylene monomers ( 2a – d ) and 10,12-tricosadiyn-1-oic acid gave the corresponding polydiacetylene derivatives ( 4a – d and 5 ), respectively. Rubidium salts of ( 4c ) and ( 4d ), a barium salt of ( 4c ), and a potassium salt of ( 5 ) were prepared and isolated; soluble potassium salts of the carboxylic acid polymers ( 4 ) were generated in aqueous solution. The effects of changes in pH on the UV/visible absorption spectra of aqueous solutions of selected carboxylic acid polydiacetylenes have been recorded, and are discussed.     

Determination of instantaneous corrosion rates and runoff rates of copper from naturally patinated copper during continuous rain events

Instantaneous corrosion rates of naturally patinated copper of varying age (16 months, 138 and 145 years) have been determined during continuous rain events in the laboratory with electrochemical impedance spectroscopy using a two-electrode cell. The two-electrode cell was found to yield the same information in bulk rainwater as a conventional three-electrode cell.Relatively constant corrosion rates, between 0.2 and 0.6 μm/y, were determined for samples having a two-layer structure with an inner brownish layer of cuprous oxide and an outer greenish layer of basic copper salts (138, 145 years). Samples with cuprous oxide as the dominating phase of the patina (16 months) showed higher and somewhat increasing corrosion rates during a rain event (from 0.6 to 1.2 μm/y). During a continuous rain event, corrosion rates were found to be approximately 10 (brownish patina) and 25 times (greenish patina) lower than corresponding instantaneous runoff rates. The first flush phenomena of the runoff process, with an increased concentration during first flush and a relatively constant concentration during steady state, was indirectly seen as an increase in solution conductivity during the first rain volume followed by relative constant value. The contribution of the concentration in the first flush to the total annual runoff rate was significant for panels having a greenish layer (138, 145 years) whereas it was negligible for panels having a brownish layer (16 months).     

伪波阻抗反演在准噶尔盆地永进油田储层描述中的应用

永进油田目的层产状平缓,断层不发育,储层厚度小、埋深大、描述困难。运用伪波阻抗技术对该区的储层进行了研究,取得了较好的效果。     

Extracting Electron Densities in N-Type GaAs From Raman Spectra: Theory

In this paper, we present the theory for calculating Raman line shapes as functions of the Fermi energy and finite temperatures in zinc blende, n-type GaAs for donor densities between 10¹⁶ cm⁻³ and 10¹⁹ cm⁻³. Compared to other theories, this theory is unique in two respects: 1) the many-body effects are treated self-consistently and 2) the theory is valid at room temperature for arbitrary values of the ratio R = (Q²/α), where Q is the magnitude of the normalized wave vector and α is the normalized frequency used in the Raman measurements. These calculations solve the charge neutrality equation self-consistently for a two-band model of GaAs at 300 K that includes the effects of high carrier concentrations and dopant densities on the perturbed densities of states used to calculate the Fermi energy as a function of temperature. The results are then applied to obtain the carrier concentrations from Fermi energies in the context of line shapes in Raman spectra due to the coupling between longitudinal optical phonons and plasmons. Raman measurements have been proposed as a non-destructive method for wafer acceptance tests of carrier density in semiconductor epilayers. The interpretation of Raman spectra to determine the majority electron density in n-type semiconductors requires an interdisciplinary effort involving experiments, theory, and computer-based simulations and visualizations of the theoretical calculations.     

Dielectric Resonators for the Measurement of Superconductor Thin Films Surface Impedance in Magnetic Fields at High Microwave Frequencies

We present the design and realization of cylindrical dielectric resonators operating in the 40–60 GHz frequency range, designed for the measurement of the surface resistance and of the surface reactance shift in High-T _c Superconductors (HTS) thin films in a dc magnetic field. The resonators are single tone, based on the TE ₀₁₁ mode, and multiple tone, the latter allowing in principle to exploit the simultaneous determination of the surface impedance at different frequencies. As an application example, we report the temperature and field dependencies of the effective surface impedance of some cuprate superconductors thin films. The results are compared with those obtained through the use of a standard metal cavity with a similar Q-factor and operating in the same frequency range. The comparison highlights a superior stability and a higher sensitivity, resulting in an increase of about two orders of magnitude in the resolution of the surface impedance measurement. By contrast, the dissipative part of the superconducting transition (above T/T _c = 0.97) is better studied with the metal cavity. We also present measurements in the vortex state in YBaCa₂Cu₃O_7−δ and Tl₂Ba₂CaCu₂O_8+x that show significantly different physics. PACS: 74.25 Nf.