Design of a novel compact modified‐circular printed antenna for high data rate wireless sensor networks

This paper presents a novel compact circular patch Ultrawideband (UWB) antenna for sensor node applications. The microstrip‐fed low‐profile antenna comprises an elliptical ring slot, two crescent‐shaped slots and two dumbbell‐shaped slots in feedline. The antenna miniaturization is achieved by a novel combination of an elliptical ring slot, two crescent‐shaped slots in circular patch. The proposed prototype has been fabricated on inexpensive FR4 substrate and the relative permittivity is (ε_r = 4.3) with 1.6 mm thickness. The overall size of the proposed miniaturized antenna is about (0.1 λ_r × 0.15 λ_r), where λ_r is the resonating wavelength of the lowest UWB frequency (ie, 3.1 GHz). The measured radiation performances of the proposed antenna are nearly an omnidirectional pattern in H‐plane and bidirectional pattern in E‐plane for all the frequencies in the whole UWB band. The development process of the antenna, radiation properties and group delay is completely analyzed and discussed.     

Effect of Gas Composition on Nitriding and Wear Behavior of Nitrided Titanium Alloy Ti-15V-3Cr-3Al-3Sn

Titanium alloy, Ti-15V-3Cr-3Al-3Sn was nitrided at different temperatures with low pressure plasma with 100% nitrogen, and nitrogen diluted with hydrogen and argon. The nitrided layers were characterized for hardness, structure, and composition. Nitrided samples show weight gain that depended on temperature and duration of nitriding. EDS results show that intake of nitrogen is significant at temperatures above 750 °C. Hydrogen dilution increases intake of nitrogen. Samples nitrided with hydrogen dilution have lower surface roughness and higher nitrogen concentration. Depth profiling by XPS shows the formation of nitride in the near-surface region and also that nitrogen concentration in the interior of the nitrided layers is higher at higher temperatures. Micro Raman shows that formation of nitride takes place at higher temperatures. XRD shows that the nitrided layers consist predominantly of alpha Ti and Ti₂N. This is reflected in the hardness increase and hardness profile in the nitrided samples. The low intake of nitrogen by the alloy is attributed to the low solubility of nitrogen in beta alloy and low diffusion coefficient of nitrogen. Reciprocating wear studies showed a lower coefficient of friction and lower wear loss for nitrided samples compared to that of substrate.     

Optimum eddy current excitation frequency for subsurface defect detection in SQUID based non-destructive evaluation

Detailed experimental studies have been carried out for the determination of optimum eddy current excitation frequencies for the defects located at different depths below the top surface of an aluminum plate. These subsurface defects were detected by using a highly sensitive superconducting quantum interference device (SQUID) based eddy current non-destructive evaluation (NDE) system. The signal to noise ratio was found to be significantly higher at the optimum excitation frequency, which depended on the depth of the defect. The optimum excitation frequencies have been evaluated for defects located at different depths from 2 to 14 mm below the top surface of the plate. The defect depth was varied in steps of 2 mm, while the overall total thickness of the stack of plates was kept constant at 15 mm. Each defect represented a localized loss of conductor volume, which was 60 mm in length, 0.75 mm in width and 1 mm in height. The experimental results show that the square root of the optimum excitation frequency is inversely proportional to the depth of defect.     

Correlation between micro-structural properties and ionic conductivity of Li1.5Al0.5Ge1.5(PO4)3 ceramics

We report on the structure and lithium ion transport properties of Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP). This material is commercially available and is prepared as amorphous powders via a flame spray technique called Flash Creation Method (FCM). We crystallize and sinter the amorphous powders at different temperatures in order to alter grain size and grain boundary properties. The structure is then characterized by means of powder X-ray diffraction, atomic force microscopy, scanning electron microscopy and transmission electron microscopy with energy dispersive X-ray spectroscopy. AC impedance spectroscopy is used to study lithium ion transport. A maximum total conductivity of 2 × 10⁻⁴ S cm⁻¹ at room temperature is found for a sample sintered at 750 °C for 2 h. In order to distinguish between grain and grain boundary contributions to the impedance spectra, equivalent circuit fits are carried out. The results are analysed in the framework of the classical brick layer model and of a finite-element approach taking into account non-ideal grain contacts. Our experimental results for the grain and grain boundary resistances are in good agreement with the predications of the finite-element approach.     

The anode performance of the hard carbon for the lithium ion battery derived from the oxygen-containing aromatic precursors

The hard carbon is attractive for the Li ion secondary battery because of its higher capacity than the theoretical value of 372 Ah kg⁻¹ based on the composition of stage 1 Li-intercalated graphite, LiC₆. However, the structure of hard carbon as an anode has not been optimized and the reaction mechanism also has not been clarified in detail. In the present study, the structure of hard carbon derived from oxygen-containing coal tar pitch was investigated by X-ray diffraction, small angle scattering and density measurement, and the relationship between the structure of hard carbon and its anode performance was discussed.     

Video indexing based on mosaic representations

Video is a rich source of information. It provides visual information about scenes. This information is implicitly buried inside the raw video data, however, and is provided with the cost of very high temporal redundancy. While the standard sequential form of video storage is adequate for viewing in a movie mode, it fails to support rapid access to information of interest that is required in many of the emerging applications of video. This paper presents an approach for efficient access, use and manipulation of video data. The video data are first transformed from their sequential and redundant frame-based representation, in which the information about the scene is distributed over many frames, to an explicit and compact scene-based representation, to which each frame can be directly related. This compact reorganization of the video data supports nonlinear browsing and efficient indexing to provide rapid access directly to information of interest. This paper describes a new set of methods for indexing into the video sequence based on the scene-based representation. These indexing methods are based on geometric and dynamic information contained in the video. These methods complement the more traditional content-based indexing methods, which utilize image appearance information (namely, color and texture properties) but are considerably simpler to achieve and are highly computationally efficient     

Precipitation in CdTe crystals studied through mie scattering

Below gap optical losses in as-grown n-type CdTe crystals were analyzed in terms of free carrier absorption and Mie extinction due to Te precipitates. Experimental absorption spectra measured between 2 to 20 μm exhibited the well-known free carrier absorption behavior α_FCA∼λ^x with x=3 due to scattering by polar optical phonons. In shorter wavelength regions below 6 μm, however, additional contributions to the light loss due to absorption and scattering by precipitates were also observed. Assuming a log-normal size distribution, the precipitate extinction spectra were calculated according to Mie theory within the electric and magnetic dipole and electric quadrupole approximation. A comparison with the experimental spectra identifies the precipitates and enables estimation of their sizes and total number density. In this investigation, both undoped and In-doped CdTe crystals grown from stoichiometric melts by vertical asymmetric Bridgman method were used. It was found that In doping, in general, suppresses Te precipitation. At high doping level (melt containing∼10¹⁹ In atoms cm⁻³), the formation of In₂Te₂ is also indicated. It is demonstrated that the Mie extinction analysis offers an, expedient method to rapidly analyze the precipitates in CdTe and in similar other wide gap materials in a nondestructive manner.     

Serologic prevalence of Toxoplasma gondii in chickens in Madras, India

Serum samples from 185 chickens (Gallus gallus) collected from the various slaughter markets in and around Madras City, India were examined for antibodies to Toxoplasma gondii using the modified agglutination test incorporating mercaptoethanol. Antibodies (> or = 1:25) to T. gondii were found in 39.5% of sera. Antibody titers of individual sera (% in parentheses) were 1:25 (8.1%), 1:50 (10.8%), 1:100 (6.5%), 1:200(2.7%), 1:400 (4.3%), 1:800 (5.9%) 1:1,600 (0.5%), and 1:3,200 (0.5%).