Double MOS Loaded Circular Microstrip Antenna with Airgap for Mobile Communication

A novel model of a wide frequency range double MOS loaded circular microstrip patch antenna with airgap between ground plane and substrate is proposed. In this structure two metal oxide semiconductor (MOS) devices are loaded on the patch to enhance the operating frequency range of antenna. To investigate the antenna, different parameters such as resonance frequency, input impedance, frequency agility, VSWR, radiation pattern etc. are calculated and simulated. The resonant frequency of proposed 10 mm radius patch is upward shifted from 5.2 to 6.8 GHz using 1 mm airgap and by loading MOS, antenna can be tuned down to 1.27 GHz operating frequency, which leads to compactness and tunability of antenna. Proposed antenna can be tuned between 1.27 and 6.8 GHz frequency of operation which makes the antenna highly suitable for wide frequency range of mobile communication. The proposed double MOS loaded antenna possessed 82.94 % frequency agility. The antenna is worth for GPS, WLAN, UMTS, and WiMAX operations.     

Temperature dependence of processes during initial stages of oxidation of poly(acrylonitrile-co-acrylic acid) films

Poly(acrylonitrile-co-acrylic acid) films containing 1.8 percent acrylic acid as comonomer units in the copolymer were oxidized in air isothermally at different temperatures for periods of 1 and 5 hours. The physico-chemical properties such as thermogravimetry, differential scanning calorimetry, infrared spectral absorption and intrinsic viscosity were analysed for the oxidized films. The intrinsic viscosity shows that the molecules of the polymer crosslink at temperature as low as 100°C. TGA spectrum shows two regions of steep weight losses in the range of temperatures studied, one is at 275–300°C and the other at 395–485°C. The first region is the formation of ladder polymer with the elimination of NH₃, HCN and CO. The second region is due to the formation of aromatic structures with the elimination of HCN, NH₃, water vapour and higher hydrocarbons. DSC spectral analysis shows an endothermic effect up to 205°C and exothermic processes from 205–300°C with a peak at 276°C. The exothermic processes continue up to 360°C. The exothermic effect is reduced for the films oxidized at 242 and 275°C. A marked endothermic effect is noticed at 120°C for the films oxidized at 242 and 275°C. This shows that the cyclization accompanying with exothermic effect sufficiently advanced during isothermal treatment leaving less room for rapid cyclization occurring upon further heating. IR spectral data show the negative environment with a shoulder at 2210 cm^?1 which is associated with uptake of oxygen during oxidation. Distinct peaks at 810 and 1550–1700 cm^?1 are noticed for the oxidized films oxidized at 275°C which are due to the presence of conjugated double bonds of the type C ? N? C ? N. This type of conjugation is assumed in the ladder polymer.     

Grafting of ethyl acrylate onto gelatin in water-isopropanol medium

Graft copolymers were synthesized by grafting ethyl acrylate onto gelatin. The reaction was carried out in water-isopropanol medium (1:1 v/v). Reactions take place within 90 min. The resulting product is insoluble in solvents for the respective homopolymers. Presence of vinyl polymer was confirmed by IR spectra.     

Formulation, in-vitro release and therapeutic effect of hydrogels based controlled release tablets of propranolol hydrochloride

Matrix based controlled release tablets of Propranolol Hydrochloride (PHCL) were formulated using hydroxy propyl methyl cellulose (HPMC), sodium carboxy methyl cellulose (sod. CMC) and their combinations. The in-vitro dissolution kinetics revealed a zero order release for selected drug, HPMC and sod. CMC combination. The selected formulation was evaluated in mongrel dog by recording the isoprenaline induced tachycardia and measuring the inhibition of tachycardia. The results showed the sustaining therapeutic effect of the formulation.     

基于汽车正面碰撞的吸能盒设计及优化

对汽车正面碰撞有限元模型进行了分析,建立了可替代整车碰撞模型的子模型,并对其进行验证。在所建立的子模型的基础上,设计出了双层波纹管样式的吸能盒结构,利用自适应响应面法对其厚度进行优化设计。整车碰撞仿真结果表明:吸能盒结构吸收的能量比原结构提高了14.2%,纵梁碰撞力比原结构减小了15.3%。     

Sixth-order differential Sallen-and-Key switched capacitor LPF using a-IGZO TFTs

This paper presents sixth-order fully differential active low pass RC and switched-capacitor (SC) filters using N-type IGZO thin-film transistors for flexible wearable continuous health monitoring systems. As a first step, a low-gain amplifier using a diode-connected load and a fully differential amplifier is designed with positive feedback based on capacitor bootstrapping. These amplifiers present a gain around 5.03 and 40 dB, respectively, whereas their respective GBW product are around 450 and 200 kHz. Then these amplifiers are employed to realize biquads, with which a sixth-order Sallen-Key low-pass RC and SC filters are implemented. The SC filter realized with low-gain DDA has shown a simulated THD of −30.9 dB, SFDR of 30.1 dB, and a power consumption of 456 μW. On the other hand, the SC filter presents a THD of −31.4 dB, SFDR of 32.2 dB, and a power consumption of 573 μW with high-gain differential difference amplifier (DDA) when a power supply of 10 V is used. Circuit simulations have been carried out in Cadence Virtuoso using in-house IGZO TFT models.     

Low power ring oscillator for IoT applications

In order to scale with the demand of higher data rates and improved spectral efficiency in next generation wireless communication systems, a large-scale multiple-input and multiple-output (MIMO) technology called massive MIMO has been proposed. In massive MIMO, appropriate signal-to-noise ratio (SNR) values can be achieved by the addition of base station (BS) antennas in place of increasing transmit power. Pilot-based channel estimation is widely used in conventional MIMO systems, where pilot signal sequences are sent from the user terminals (UTs) to the BS to estimate the channel. In massive MIMO-based cellular networks, channel estimation in a given cell will be impaired by the pilot signal sequences transmitted by users in other cells—rendering the addition of antennas or transmit power ineffective. This effect is called pilot contamination. Therefore, pilot-based channel estimation limits the performance of massive MIMO. Semi-blind and blind methods are alternatives to pilot-based channel estimation that perform channel estimation with short pilot signal sequences and without pilot signal sequences, respectively. Blind channel estimation is one of the promising solutions to the pilot contamination problem in massive MIMO. This paper compares, using MATLAB simulations of a cluster-based COST 2100 channel model, the performance of pilot-based, semi-blind, blind, and adaptive-blind channel estimation methods. The pilot contamination effect on different channel estimation methods and how channel estimation methods can be used to overcome pilot contamination are shown. Finally, an adaptive independent component analysis (ICA)-based channel estimation method, which outperforms conventional ICA in terms of computational complexity, is proposed.     

Design and Analysis of Low Noise Optimization Amplifier Using Reconfigurable Slotted Patch Antenna

Now a days, the communication between different nodes in a Mobile Ad hoc Network (MANET) is not guarded. Various encryption mechanisms are used to protect the communication between nodes. Link failures and packet dropping due to unfaithful nodes are becoming one of the main opposition for the trusted detection of malicious nodes. A failure can occur either due to channel errors or harmful nodes in network. These attacks may have the intention of modifying the routing protocol so that the data transmission through a specific node controlled by the attacker disturbs the network topology. Thus it deteriorates the performance of network. Mutual association of dropped packets is capitalized for synthesizing the suspicious nodes in MANET. The algorithm proposed is using an efficient cryptosystem with cipher text list validator scheme and a communal auditing scheme for the validation of certificate received from individual nodes. For constructing the framework, the proposed algorithm with five phases has a network setup phase, data routing phase, communal auditing phase, error node detection phase and a data receiver phase. This framework makes the MANET node build a safe routing topology by effectively judging the harmful nodes as well as the unfaithful information accepted from supplementary nodes.     

Thermoresponsive MALDI probe surfaces as a tool for protein on-probe purification

Thin film depositions of rf plasma polymerized N-isopropylacrylamide (ppNIPAM) show a phase transition temperature below which the polymer surface is hydrophilic, and protein nonadsorptive, and above which the polymer surface is hydrophobic, and protein-retentive. Results presented here demonstrate that this thermoresponsive plasma polymer can be coated on the surface of a MALDI probe and subsequently used for on-probe biomolecule cleanup. Specifically, a contaminated biomolecule can be applied to the ppNIPAM coated MALDI probe surface at a temperature above the phase transition temperature, washed using solvent also held above the phase transition temperature, and then analyzed by reducing the probe temperature to room temperature before adding the MALDI matrix. With the use of this approach, it is demonstrated that cytochrome c contaminated with 0.3% SDS, which yields only a very weak MALDI ion signal as directly deposited, can be purified on-probe using the thermoresponsive plasma polymer to improve significantly the ion signal. It is further shown that the decontamination of whole cell protein extracts from cyanobacteria is augmented through the use of the ppNIPAM coated MALDI probe.     

Investigations on polyurethane ionomers. II. 3,4-dihydroxycinnamic acid-based anionomers

Polyurethanes of different compositions were synthesized by chain extending the prepolymer formed by the reaction of various polyols and diisocyanate with 3,4-dihydroxycinnamic acid. The polyurethanes were converted to their anionomers by treating with metal acetates. The polyurethanes were characterized using FTIR, FTNMR, TGA, and DSC analysis. The molecular weights of the polymers were determined using GPC. A detailed study of the effect of variation of molecular weight of the polyols and mol ratio of the various reactants on the glass transition temperature and molecular weight of the polyurethanes was made. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2105–2109, 1997