Comparison of p–n junction formed by BF2 and B implantation in silicon microstrip detector with low and high thermal budget: impact of fluorine on electrical characteristics

The influence of crystal damage on the electrical properties and the doping profile of the implanted p⁺–n junction has been studied at different annealing temperatures using process simulator TMA-SUPREM4. This was done by carrying out two different implantations; one with implantation dose of 10¹⁵ BF₂⁺ ions/cm² at an energy of 80 keV and other with 10¹⁵ B⁺ ions/cm² at 17.93 keV. Substrate orientation 1 1 1 of phosphorus-doped n-type Si wafers of resistivity 4 kΩ cm and tilt 7° was used, and isochronally annealing was performed in N₂ ambient for 180 min in temperature range between 400°C and 1350°C. The diode properties were analysed in terms of junction depth, sheet resistance. It has been found that for low thermal budget annealing, boron diffusion depth is insensitive to the variation in annealing temperature for BF₂⁺-implanted devices, whereas, boron diffusion depth increases continuously for B⁺-implanted devices. In BF₂⁺-implanted devices, fluorine diffusion improves the breakdown voltage of the silicon microstrip detector for annealing temperature upto 900°C.For high thermal budget annealing, it has been shown that the electrical characteristics of BF₂⁺-implanted devices is similar to that obtained in B⁺-implanted devices.     

Poly (3‐hydroxybutyrate)/cellulose nanocrystal films for food packaging applications: Barrier and migration studies

This article reports the fabrication of poly (3‐hydroxybutyrate) (PHB)/cellulose nanocrystal (CNC) based nanobiocomposite films with improved gas barrier and migration properties for food packaging applications. Acid hydrolysis of cellulose pulp from bamboo (Bambusabalcooa) yields CNCs with diameter of 15–20 nm and length of 400–600 nm. Evaluation of d‐spacing using XRD indicates intercalation of PHB matrix with CNC at optimum loadings of 2 wt%. Overall migration values in presence of both polar and nonpolar food simulants are found within standard limits. After migration studies on PHB/CNC films, significant decrease in crystallization temperature (by 15°C) is observed, with subsequent presence of multiple melting peaks. The oxygen transmission rate (OTR) decreases significantly (by ～65%), even at low CNC (～2 wt%) loadings. Permeation activation energy (calculated from Arrhenius equation) and barrier properties, such as solubility and diffusivity, improved (decreased by ～57 and 17%, respectively) with loading fractions (～2 wt%) due to the hydrogen bonded interaction of PHB with CNCs as well as tortuous path provided towards oxygen permeation. POLYM. ENG. SCI., 55:2388–2395, 2015. © 2015 Society of Plastics Engineers     

Dielectric and piezoelectric properties of PVDF/PZT composites: A review

Smart materials, which exhibit piezoelectricity, find an eclectic range of applications in the industry. The direct piezoelectric effect has been widely used in sensor design, and the inverse piezoelectric effect has been applied in actuator design. Ever since 1954, PZT and BaTiO₃ were widely used for sensor and actuator applications despite their toxicity, brittleness, inflexibility, etc. With the discovery of PVDF in 1969, followed by development of copolymers, a flexible, easy to process, nontoxic, high density alternate with high piezoelectric voltage coefficient was available. In the past 20 years, heterostructural materials like polymer ceramic composites, have received lot of attention, since these materials combine the excellent pyroelectric and piezoelectric properties of ceramics with the flexibility, processing facility, and strength of the polymers resulting in relatively high dielectric permittivity and breakdown strength, which are not attainable in a single phase piezoelectric material. The current review article is an attempt to provide a compendium of all the work carried out with reference to PVDF‐PZT composites. The review article evaluates the effect of grain size, content and other factors under the purview of dielectric and piezoelectric properties while evaluating the sensitivity of the material for sensor application. POLYM. ENG. SCI., 55:1589–1616, 2015. © 2015 Society of Plastics Engineers     

Design,Synthesis, and Evaluation of an 18F‐Labeled Radiotracer Based on Celecoxib–NBD for Positron Emission Tomography (PET) Imaging of Cyclooxygenase‐2 (COX‐2)

A series of novel fluorine‐containing cyclooxygenase‐2 (COX‐2) inhibitors was designed and synthesized based on the previously reported fluorescent COX‐2 imaging agent celecoxib–NBD ( 3 ; NBD=7‐nitrobenzofurazan). In vitro COX‐1/COX‐2 inhibitory data show that N‐(4‐fluorobenzyl)‐4‐(5‐p‐tolyl‐3‐trifluoromethylpyrazol‐1‐yl)benzenesulfonamide ( 5 ; IC₅₀=0.36 μM , SI>277) and N‐fluoromethyl‐4‐(5‐p‐tolyl‐3‐trifluoromethylpyrazol‐1‐yl)benzenesulfonamide ( 6 ; IC₅₀=0.24 μM , SI>416) are potent and selective COX‐2 inhibitors. Compound 5 was selected for radiolabeling with the short‐lived positron emitter fluorine‐18 (¹⁸F) and evaluated as a positron emission tomography (PET) imaging agent. Radiotracer [¹⁸F] 5 was analyzed in vitro and in vivo using human colorectal cancer model HCA‐7. Although radiotracer uptake into COX‐2‐expressing HCA‐7 cells was high, no evidence for COX‐2‐specific binding was found. Radiotracer uptake into HCA‐7 tumors in vivo was low and similar to that of muscle, used as reference tissue.     

A Pulsed UWB Receiver SoC for Insect Motion Control

A 2.5 mW wireless flight control system for cyborg moths is presented, consisting of a 3-to-5 GHz non-coherent pulsed ultra-wideband receiver system-on-chip with an integrated 4-channel pulse-width modulation stimulator mounted on a 1.5 cm by 2.6 cm printed circuit board. The highly duty cycled, energy detection receiver requires 0.5-to-1.4 nJ/bit and achieves a sensitivity of -76 dBm at a data rate of 16 Mb/s (10^-3 BER). A multi-stage inverter-based RF front end with resonant load and differential signal chain allow for robust, low energy operation. Digital calibration is used in the baseband amplifier, ADC and DLL to cancel voltage and timing offsets. Through the use of a flexible PCB and 3-D die stacking, the total weight of the electronics is kept to 1 g, within the carrying capacity of an adult Manduca sexta moth. Preliminary wireless flight control of a moth in a wind tunnel is demonstrated.     

An improved surface roughness prediction model using Box-Cox transformation with RSM in end milling of EN 353

Journal of Mechanical Science and Technology - In the present work, an attempt has been made to use Box-Cox transformation with response surface methodology to develop improve surface roughness...     

Ant colony optimization for group technology applications

The problem of grouping of parts into part-families and that of machines into machine-cells has attracted the attention of many researchers particularly for medium variety of parts with medium production volume requirement, which traditionally required their production in batches for achieving economics of production. This kind of grouping, consequently offering benefits of mass production, was aimed to have independent cells processing ideally almost different sets of part-types. For this purpose, a number of approaches are available from various kinds of heuristics to mathematical programming formulations. Evolutionary methods such as neural network, genetic algorithm, and simulated annealing have also been tried and have been found to provide better grouping solutions with much less computational complexity. In the present paper, ant colony optimization approach with number of newer strategies, incorporating more generalised framework of ants’ behaviour, has been applied to the parts and machines grouping problems taken from the literature. The results obtained from their application were found to be encouraging and thus establish the usefulness of the proposed approaches. Average performance of Tabu search with multiple ants was found to be the best and thus the parameter values for this approach were also determined using design of experiments methodology.     

Study of effect of covalency in heavy rare-earth monoantimonides upto 31 GPa

In the present paper, we have investigated the high-pressure structural phase transition of rare earth antimonides (HoSb and TmSb). A modified interaction potential model (MIPM) (including the covalency effect) has been developed. Phase transition pressures are associated with a sudden collapse in volume. At compressed volumes, these compounds are found in CsCl phase. The phase transition pressures and associated volume collapses obtained from present potential model show a generally good agreement with available experimental data and others. The elastic constants and bulk modulus are also reported. Our results are in general in good agreement with experimental and theoretical data where available, and provide predictions where they are unavailable.