Electrical conductivity and dielectric loss in doped Pb(NO3)2 single crystals

dc ionic conductivity measurements were made on single crystals of Pb(NO₃)₂ doped with monovalent Na⁺ and K⁺ in the temperature range of 100–400°C. In the extrinsic region the conductivity was found to decrease with Na⁺ having a smaller ionic size, and to increase with K⁺ with larger ionic size compared to the host Pb ion. Conductivity is attributed to the mobility of anti-Frenkel defects as in the case of PbF₂. Dielectric loss measurements were made on the Pb(NO₃)₂: K⁺ system in the frequency range of 300 Hz to 20 kHz at different temperatures. Impurity vacancy pairs of the type K⁺-(NO^-₃)_V are found to be responsible for the observed dielectric loss peaks. The maximum peak frequency is found to increase with temperature.     

On Totally Ordered Rings Whose Positive Cones are Finitely Generated

This paper is mainly dealt with the structure of totally ordered rings (t.o. rings) whose positive cones are finitely generated as multiplicative right ideals.AMS Subject Classification (1991): 16W80, 13J25     

Preparation and electrical characterization of (PVC + KBrO3) polymer electrolytes for solid state battery applications

This paper presents results of studies on dc electrical conductivity and transference number measurements on potassium bromate (KBrO₃) complexed polyvinyl chloride (PVC) films prepared by solution cast technique. Temperature dependence of dc electrical conductivity and transference number data indicated the dominance of ion type charge transport in these specimens. The magnitude of conductivity increased with increase in concentration of the salt and temperature. Using this (PVC + KBrO₃) electrolyte, solid-state electrochemical cells were fabricated, and their discharge profiles were studied under a constant load of 100 kΩ. Several cell profiles such as open circuit voltage, short circuit current, power density, and energy density associated with these cells were evaluated and were reported. The features of complexation of the electrolytes were studied by X-ray diffraction and Fourier transform infrared spectroscopy. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006     

Magnetic-field-induced valence transition in rare-earth systems

The magnetic-field-induced valence transition in rare-earth systems has been investigated using the periodic Anderson model supplemented by the Falicov-Kimball term. This model has been solved by first decoupling the Falicov-Kimball term as proposed by Khomskii and Koharjan and then taking the limit of infinite intra-site Coulomb repulsion. The valence transition both in the absence and in the presence of magnetic field as a function of temperature is studied. It has been found that the system makes transition from non-magnetic to magnetic state when the magnetic field increases beyond a critical value H _c. The phase boundary defined in terms of reduced field H _c(T)/H _c(0) and reduced temperature T/T _v (T _v being the valence transition temperature in the absence of field) is almost independent of the position of the localized level. The results are in qualitative agreement with experimental observations in Yb- and Eu-compounds.     

Long-term stability of InP MIS devices

Room-temperature bias stress measurements were performed on n-type InP MIS capacitors. A wide range of interface passivation processes and gate dielectrics was investigated. A generally observed behaviour under positive bias stress is a slow trapping - fast detrapping consistent with a trap distribution in the interfacial layer above the conduction band edge of InP. Large variations both in the magnitude and in the time dependence of the flat-band voltage shift ΔV_FB are observed. We discuss these drift behaviours in terms of interface traps - rather than bulk dielectric traps - in relation with the physico-chemical properties of the interface. It is shown that devices based on InP treated by annealing under arsenic pressure and controlled oxidation exhibit a very good stability. For any passivation procedure, the drift is strongly diminished if the device is stressed with AC voltage compared to DC voltage.     

The dynamic analysis of circular plates and shallow spherical shells

In the investigation reported here an attempt has been made to study the influence of Berger's approximation on the non-linear transient response of circular plates and shallow spherical shells. The governing equations of motion obtained from Berger's approximation are solved by using the rapidly converging Chebyshev series spacewise and the Houbolt scheme for integration in the time domain. Results calculated when using Berger's approximation are compared with exact results. It is shown that Berger's method yields very accurate values for plates and shells under transient loading, in the case of immovable edge conditions.     

圆合成孔径声呐多点定位运动补偿

圆合成孔径声呐(CSAS)的成像性能受平台运动误差影响而下降,利用单侧回波可估计CSAS基阵的斜距误差,但单侧回波在小测绘带时无法估计升沉误差,针对此问题,提出了一种利用单侧回波信号的声呐平台三维运动估计和补偿方法。首先,对CSAS在不同观测角度的目标回波取极大值获得目标回波的到达时间;其次,基于多个点目标的到达时间建立CSAS三维定位模型;然后利用列文伯格-马夸尔特方法对声呐三维坐标进行估计;最后将位置估计结果与时域反投影成像方法结合实现对目标的成像.仿真结果表明:该方法能精确估计声呐平台运动误差,其空间坐标的估计误差小于仿真信号波长的1/8,从而精确补偿了CSAS在不同空间采样点上的阵元回波时间差,显著提高了目标成像质量。湖上试验结果表明,该算法能够实现对CSAS的运动误差补偿。仿真和试验结果均验证了方法的可行性和有效性。     

Gold‐Nanoparticle‐Decorated Boron Nitride Nanosheets: Structure and Optical Properties

Synergetic cooperation of individual components of the nanocomposites (NCs) is responsible for their novel properties that lead to various technological applications. A simple chemical process depicting the deposition of functionalized gold nanoparticles on the surface of boron nitride nanosheets (BNNSs) in solution is reported. The structure, chemical composition, and optical properties of nanosheets are systematically studied. The deposition of Au nanoparticles on BNNS (BNNS_Au) results in plasmonic band modulation, thus altering the optoelectronic properties of BNNSs. The intense surface plasmon absorption band of BNNS_Au is narrowed and red‐shifted relative to the absorption band of as synthesized monometallic BNNSs. The observations reflect the strong interfacial interaction between BNNS and Au nanoparticles. This approach constitutes a basis for a simple process leading to the preparation of functionalized BNNSs and their utilization as nanoscale templates for assembly and integration with other nanoscale materials for futuristic optoelectronic devices.