Electrical impedance investigation of gamma-irradiated TlInS2〈5%C〉 crystals

In this article, the authors carry out a pioneering study of monocrystalline TlInS[Formula: see text] at higher than room-temperatures using impedance spectroscopy. It is shown that in TlInS[Formula: see text] crystals at temperatures higher than 400 K, the nature of conductivity is predominantly ionic. Moreover, characteristics of impedance spectra behavior of TlInS[Formula: see text] monocrystal samples were studied using the measurement frequency range of 25–106 Hz. For the measured frequency range, it is shown that curves of active and reactive impedance components undergo a dispersion characterized by decreasing values of [Formula: see text] and [Formula: see text], as the frequency of the electric field and radiation dose increases.

Registration of geomagnetic field variations with a magnetic modulating sensor

Показана возможность применения магнитомодуляционных датчиков слабого магнитного поля с аморфным ферромагнитным сердечником, работающих в режиме автопараметрического усиления сигнала магнитной индукции, для измерения амплитуды и фазы вариаций геомагнитного поля в диапазоне частот 0,01–30 Гц. Разрешающая способность магнитомодуляционных датчиков с автопараметрическим усилением сигнала магнитной индукции в аморфном ферромагнитном сердечнике с компенсированной продольной магнитострикцией не превышает 1 пТл. Приведены примеры синхронной записи амплитуды трех составляющих вариаций геомагнитного поля на различных участках диапазона измеряемых частот, записанные во время слабой магнитной бури интенсивностью 5 баллов. Получаемая с помощью магнитомодуляционного датчика информация об амплитуде и фазе геомагнитных вариаций совместно с данными по амплитуде электрического поля электромагнитных волн может быть применена в геофизике в различных методах магнитотеллурического зондирования. The possibility of using magnetic modulating sensors of the weak magnetic field with amorphous ferromagnetic core operating in the mode of autoparametric signal gain of magnetic induction to measure the amplitude and phase variations of the geomagnetic field in the frequency range 0.01–30 Hz. Resolution of magnetomodulation sensors with autoparametric signal increase of magnetic induction in ferromagnetic amorphous core with offset longitudinal magnetostriction is not more than 1 pTl. Examples of synchronous recording of the amplitude of the three components of the variations of the geomagnetic field in different parts of the measured frequency range, recorded during a weak magnetic storm intensity of five points are given. Information obtained by magnetomodulation sensor about the amplitude and phase of geomagnetic variations, together with data on the amplitude of the electric field of electromagnetic waves can be applied in geophysics to the different methods of magnetotelluric sounding.

Very Low Crosstalk Measurement of Substrate Integrated Coaxial Line (SICL)

When designing a microwave circuit involving substrate integrated coaxial lines (SICLs), it is important to know what real crosstalk between SICLs is. A measured crosstalk will be a good reference value in a practical design. In addition, it is also needed to compare and check the crosstalk from the simulation and calculation formula with measured results. However, it is very difficult to measure the crosstalk between SICLs because it is theoretically very low. In this study, for the first time, the crosstalk characteristics of a SICL are evaluated through experimental design and measurements. By adjusting the layout of the structures and implementing controlled experiments, interference caused by the presence of leaks and radiation at the interface and structural transitions is effectively suppressed. The experimental results show that for two parallel SICLs with a length of 30 mm and an interval of 5 mm, the isolation is greater than 80 dB for the measured frequency range of 1–8 GHz, significantly better than the results of the grounded coplanar waveguide (GCPW).

Janus-like Fe3O4/PDA vesicles with broadening microwave absorption bandwidth

Fe3O4/PDA vesicle Janus nanospheres were successfully synthesized, and they exhibited an ultra-wide effective band as wide as 11.6 GHz, covering 73% of the whole measured frequency range (2–18 GHz), and a strong absorption intensity as high as −50.0 dB due to the asymmetric polarization and magnetic coupling effect.

Waveguide Slot Array Antenna with a Hybrid-Phase Feed for Grating Lobe Reduction

The design of a 112-element millimeter-wave waveguide slot array antenna to reduce the grating lobe level is presented. A hybrid-phase feeding technique combining a cophase feed and an alternating-phase feed is applied to facilitate the suppression of grating lobes. In addition, a stepped feed waveguide and offset coupling slots aligned in a line are employed to realize a tapered aperture distribution. As a result, grating lobe suppression of 8.1 dB was achieved on the diagonal planes compared to a conventional alternating-phase-fed waveguide slot array antenna. A prototype of the proposed antenna was fabricated and measured. The measured results show that the proposed antenna exhibits a −15 dB reflection bandwidth of 3.4%and an average realized gain of 26.72 dBi within the measured frequency range. Good agreement between the simulated and measured radiation patterns is also observed.

Dielectric characteristics of Fe-doped LaTiO3+δ and visible light modulation

Fe-doped La1−xFexTiO3+δ (x = 0.05, 0.1, and 0.3, 0.4) ceramic samples were prepared via traditional solid-state reaction route, in which the dielectric properties of visible light modulation were found at room temperature in the measured frequency range.

Multiferroic Properties of Nanopowder-Synthesized Ferroelectric-Ferromagnetic 0.6BaTiO3-0.4NiFe2O4Ceramic

Multiferroic 0.6BaTiO3-0.4NiFe2O4dense nanoceramic composites were synthesized via a powder-in-sol precursor hybrid chemical synthesis route and a ceramic sintering process. At the measured frequency range (1 kHz~1 MHz), the relative dielectric constant is 150~1670 and the dielectric loss is 0.05~0.70. The composite ceramic showed obvious coexistence of ferroelectric and ferromagnetic phases. With the increase of temperature, the saturation ferromagnetic magnetization decreases, while the ferroelectric polarization increases.

Magnetization and Microwave Absorption Properties of La0.67 Sr0.33 MnO3 with Different Particle Size

La 0.67 Sr 0.33 MnO 3 particles with different particle size have been prepared by sol-gel method. The structure, magnetization and microwave absorption properties have been investigated. The results show that the particle size can be controlled by sinter temperature. The peaks of the maximum reflection loss (RL) move to higher frequency regions with increasing particle size. The value of the maximum RL is -32 dB at 10.2GHz with a particle size of 58.5nm. The bandwidth with a RL exceeding -8dB reached 1.6GHz in the whole measured frequency range, suggesting that La 0.67 Sr 0.33 MnO 3 particles are promising for application as a wideband and strong absorption building microwave absorber.

Novel Radar Absorbing Materials with Broad Absorbing Band: Carbon Foams

Carbon foams were prepared by a polymer sponge replication method and their microwave absorbing properties were investigated in this paper. It was found that the electric conductivity of carbon foams increases quickly with the improvement of carbonization temperatures. Moreover, the electric conductivity of carbon foams strongly affects their microwave absorbing performances. As the electric conductivity increases from 0.02 S/m to 1.03 S/m, the dominant electromagnetic behavior of carbon foams changes from transmission to reflection with regard to the incident electromagnetic wave. The best microwave absorbing performance was achieved for the carbon foam with an electric conductivity of 0.46S/m when other parameters are fixed at constants, and absorbing values for the carbon foam exceeds 7dB almost in the whole measured frequency range of 4-15GHz, while the frequencies range for absorbing values exceeding 8dB are about 7 GHz, demonstrating a characteristic of broad absorbing bandwidth. It is to be noted that the absorbing characteristic for the carbon foam with an electric conductivity of 0.46S/m is obtained without any impedance match design, which indicates that carbon foams have the possibility to be applied as broad absorbing bandwidth RAMs.

An Experimental Study on the Dynamic Response of a Beam Structure Containing a Pseudo Joint

The effects of frictional damping on the dynamic response of a beam structure have been investigated. The frictional damping was contributed from the slip mechanisms in a ‘pseudo’ joint, that is a joint that did not take any static load. Using pseudo joints for vibration control has significant advantages over using joints that are designed both to take static load and to introduce frictional damping; because there is almost no restriction on the configuration of the pseudo joint, the undesirable side effects related to the frictional damping such as fretting corrosion of contact surfaces and loss of static stiffness are zero if the frictional damping from a pseudo joint is utilized. An ‘optimum’ clamping force was found which minimized the magnitude of the frequency response function (FRF) of the structure under excitation. A reduction of about 20 dB in the amplitudes of the FRFs was achieved by adjusting the clamping force at the joint. Frictional damping was found to be significant over the measured frequency range of 20-2000 Hz, and it was particularly effective over the range of 20-1000 Hz. The magnitudes of the FRFs of the structure were determined by the ratio of clamping force to excitation force. They were insensitive to the change of clamping force near its optimum value; also the optimum clamping force was not sensitive to small modifications to the structure. Therefore, utilizing frictional damping in pseudo joints is an effective technique for vibration control.