Study of structural,electromagnetic and dielectric properties of cadmium substituted Ni–Zn nanosized ferrites

Sol-gel auto-combustion method was adopted to prepare Cd²⁺ ions substituted Ni–Zn nanosized ferrites having a chemical formula Ni_0.5Zn_0.5-xCd_xFe₂O₄ (0.0 $\le x\le 0.4)$. Their structural, electromagnetic, and dielectric properties were investigated by using XRD, FE-SEM, EDS, FTIR, VSM, and IS. The XRD analysis revealed a single-phase cubic structure of all samples. The addition of cadmium increased the lattice constant and cell volume of Ni–Zn ferrite due to the difference in the ionic radii between Cadmium (0.97 ?Å) and Zinc (0.74 ?Å). FESEM images showed irregularly shaped grain sizes in the range of 40 to 73 ?nm with random orientations and some agglomeration. The FTIR analysis also confirmed the presence of spinal ferrite phase functional groups in all samples. The saturation magnetization decreased (from 89.51 to 71.32 emu/g) with increasing cadmium content. However, the remanent magnetization and coercivity parameters increased with an increase in cadmium content. The dc resistivity as a function of the temperature of all samples was investigated, and the activation energies were found to be in the range of 0.48 to 0.51 ?eV. The dielectric loss decreased with increasing cadmium content. However, the dielectric constant and dielectric loss tangent (tan) varied non-monotonically with increased cadmium content.     

A new general-purpose isothermal microcalorimeter for use at temperatures up to 200 °C

The design and some properties of a new general-purpose isothermal microcalorimeter are reported. The instrument is a twin thermopile heat conduction calorimeter, which is designed for use up to 200 °C. The calorimetric units and surrounding heat sink are suspended inside a hollow aluminium construction, which is thermostated. Above that unit a second thermostated block is positioned and the whole assembly is suspended inside a Dewar vessel. When the instrument is used at room temperature and below, the thermostated units are cooled by use of an insertion Peltier effect cooler. The instrument can be used with a wide range of different reaction vessels (diameter 14 mm). Baseline experiments have been conducted in the temperature range 15-200 °C. Typical values obtained during 10 h periods at 200 °C are ±3 and ±10 nW for the baseline drift and baseline fluctuations, respectively. The heat detection limit, determined by release of electrical energy, is about 2 μJ. Preliminary stability measurements have been conducted at 100 °C on samples of stabilised and non-stabilised polyamide film.     

Characterization of the organization in shear layers via the Proper Orthogonal Decomposition

Experiments are performed in an incompressible plane turbulent mixing layer, using various hot wire rake configurations. From these experiments, the Proper Orthogonal Decomposition is applied for kernels where the space-time correlation tensor is evaluated over different spatial meshes and velocity components configurations. The resulting decompositions are then discussed in terms of characterization of the organization of the flow for various scalar or vectorial approaches of the POD. An incrtial range law is evidenced. The instantaneous contribution of the first modes of the POD to the organization of the flow is analyzed. A dynamical behavior for the organization of the flow is observed from the correlation between the first two modes contribution.     

Method of polarization reflection matrix measurement in the submillimeter wave range

Homodyne method of measurement of polarization reflection matrix, providing the possibility of simultaneous measurement of all four complex coefficients of polarization reflection matrix in submillimeter quasi-optical (QO) circuits is presented. Technical realizability of the method for QO waveguides of the class of "hollow dielectric wavequide" is shown.     

Quantitative millimetre wavelength spectrometry at pressures approaching atmospheric: II. Determination of oxygen at atmospheric pressure

A millimetre wavelength (MMW) Fabry-Perot cavity spectrometer described in earlier work has been applied to the measurement of oxygen absorption at 60 GHz and atmospheric pressure in a gas matrix of nitrogen. The spectrometer has also been modified such that the MMW source is stabilised by a sub-harmonic microwave signal transmitted by an infrared carrier on a single mode telecommunications fibre optic. This is a step towards developing an instrument comprising minimal electronic components that can perform MMW spectrometry remotely. Oxygen determinations were achieved by monitoring the change in the quality factor (Q) of a resonant Fabry-Perot cavity due to the presence of an absorbing sample. The MMW absorption of the sample was determined by incrementing the frequency modulation (FM) deviation of the source frequency scanning the cavity resonance profile. The response curve of absorption signal versus fraction of oxygen in nitrogen was found to be linear throughout the working range of 1-100% O₂ (v/v) in N₂ with a slope of (1.407±0.007)×10⁻⁴ m⁻¹ (% O₂)⁻¹. The detection limit (3× standard deviation of the background) was found to be ∼0.8% (v/v). The MMW technique employed is advantageous since, unlike common MMW techniques, there is no vacuum requirement. Application of this method, to the monitoring of oxygen in gas mixtures of practical importance, is proposed. Values of the oxygen spectral absorption coefficients of lines between 55 and 60 GHz were measured at reduced pressure and found to be within ±2% of previous literature values. A pressure correction coefficient for O₂ absorption at 60 GHz in the 45-121 kPa range was obtained and found to be (1.354±0.014)×10⁻⁴ m⁻¹ kPa⁻¹.     

Darstellung und Kristallstruktur der Kupfer(I)-chalkogenolat-2,2′-Bipyridin-Komplexe [CuS(2,4,6-iPr3C6H2)]4(Bipy)2 und [CuSe(2,4,6-iPr3C6H2)]2(Bipy)2

Synthesis and Structure of Copper(I)Chalcogenolate-2,2′-Bipyridine Complexes [CuS(2,4,6-iPr₃C₆H₂)]₄(Bipy)₂ and [CuSe(2,4,6-iPr₃C₆H₂)]₂(Bipy)₂ The oligomeric homoleptical copper(I) chalcogenolate compounds [CuS(2,4,6-iPr₃C₆H₂)]_x=4,8 and [CuSe(2,4,6-iPr₃C₆H₂)]₆ react with 2,2′-bipyridine (Bipy) to yield the tetranuclear complex [CuS(2,4,6-iPr₃C₆H₂)]₄(Bipy)₂ ( 4 ) and the dinuclear complex [CuSe(2,4,6-iPr₃C₆H₂)]₂(Bipy)₂ ( 5 ). The structures of 4 and 5 were determined by X-ray analysis. In the eight-membered Cu₄S₄ core of 4 with chair conformation the copper atoms are linked by μ₂-bridging selenolate ligands. Only two copper atoms are coordinated by 2,2′bipyridine. The corresponding copper(I) selenolate complex ( 5 ) forms a folded four-membered Cu₂Se₂ ring with μ₂-bridging selenolate ligands. The Cu? Cu distance of 2.52 Å is relatively short. In contrast to the reaction performed with 2,2′-bipyridine, addition of phenantroline to 1 respectively 2 yields a dinuclear complex [CuS(2,4,6-iPr₃C₆H₂)]₂(Phen)₂ ( 10 ). NMR spectroskopic and cryoscopic measurement of 4 show that this complex dissociates into smaller fragments in solution which undergo rapid exchange reactions. However, corresponding investigations performed on 5 indicate that the solid state structure is maintained in solution. The electrochemical behaviour of 4, 5 and 10 was studied in CH₂Cl₂ and in any case no reversible redox processes could be observed.     

Temperature measurements by H2-CARS in the reactive zone of a plasma test reactor for hydrocarbon synthesis

The application of coherent anti-Stokes Raman spectroscopy (CARS) to an electric are test reactor is described in which acetylene synthesis in analogy to the large-scale industrial process is .studied. We report on spatially resolved measurements of H₂-CARS spectra, the comparison with calculated spectra, and the determination of temperatures in the reaction zone.Dedicated to Prof. Rudolf Wienecke on the occasion of his 65 birthday.     

Photocrosslinking of copolymers of vinyloxyethyl methacrylate–styrene initiated by sulfonium salts. I. Transient species formed on photolysis of sulfonium salt

Benzyl cation was detected by transient absorption spectroscopy with a spectroscopic multichannel analyzer on pulse excitation (fourth harmonic of Nd:YAG laser, 266 nm; 10 ns fwhm) of benzyl(4-hydroxyphenyl) methylsulfonium hexafluoroantimonate(BSS) in 1,2-dichloroethane (EDC). The benzyl cation was long-lived (lifetime, 59 ms) at room temperature and quenched by a vinyl ether compound. The formation of the benzyl cation as active species on photolysis of BSS is in contrast to the formation of Brønsted acids in other sulfonium salts so far reported. © 1992 John Wiley & Sons, Inc.     

测量不确定度的研究和应用进展

综述了测量不确定度在国内外的研究及应用的进展，发现测量不确定度是现代误差理论的重要内容，是定量描述测量结果质量的重要指标。目前由ISO等七个国际组织提出的GUM(测量不确定度表述导则)已被各国广泛接受，国内外已有大量关于不确定度应用的文献。除GUM外，还存在其它几种不确定度评定模型。我国虽然对GUM存在重大疑义，并向有关国际组织提出了一些建设性的意见，但在方法的执行上目前仍然与国际社会保持了对GUM的一致态度。     

Electron beam forming system for irradiation of large diameter cylindrical products

The report describes electron beam electromagnetic forming system, which is destined for irradiation of cylindrical long goods, specifically for PE tubes 160 mm diameter. System consists of electromagnet, power supply units, beam distributions control units, etc. for use at an electron accelerator at 5 MeV and 50 kW. The particular geometry of the magnet poles and their mutual arrangement are creating an irradiation field that allows the electrons to irradiate the surface of the product close to 90°.