Fiber-optic spark delivery for gas-phase laser-induced breakdown spectroscopy

This article reports what are to the authors' knowledge the first gas-phase laser-induced breakdown spectroscopy (LIBS) measurements using a fiber-optically delivered spark. A silver- and polymer-coated hollow fiber delivered high-energy nanosecond 1064 nm Nd:YAG laser pulses, which were focused to generate high-energy-density plasmas in ultra-lean methane-air mixtures. Emissions from these plasmas were collected and spectroscopically analyzed to quantify relative fuel-to-air ratio. These measurements were compared with others made using traditional LIBS techniques without the fiber-optically delivered spark. Similar results were obtained, but with larger shot-to-shot variability, for the case of the fiber-optically delivered spark.     

The influence of temperature on the photoluminescence properties of single InAs quantum dots grown on patterned GaAs

ABSTRACT: We report the temperature-dependent photoluminescence of single site-controlled and self-assembled InAs quantum dots. We have used nanoimprint lithography for patterning GaAs(100) templates and molecular beam epitaxy for quantum dot deposition. We show that the influence of the temperature on the photoluminescence properties is similar for quantum dots on etched nanopatterns and randomly positioned quantum dots on planar surfaces. The photoluminescence properties indicate that the prepatterning does not degrade the radiative recombination rate for the site-controlled quantum dots.     

Preparation and in vitro,bulk, and surface investigation of chitosan/graphene oxide composite films

Chitosan/graphene oxide (GO) composite films were prepared by solution blending method. Intensive characterization of films, surface, and bulk, was performed by Fourier transmission infrared spectrometry, X‐ray diffraction, scanning and transmission electron microscopy, thermal gravimetric analysis, and mechanical test. The biocompatibility of chitosan/GO films was tested in vitro on the murine osteoblastic cell line MC3T3‐E1. By incorporating 6 wt% GO into chitosan, Young's modulus and tensile strength values exceed those of nacre by about 60 and 20%, respectively. Biocompatibility assays indicated a high cell proliferation rate for the composite films with high GO content. POLYM. COMPOS., 34:2116–2124, 2013. © 2013 Society of Plastics Engineers     

Efficient rate-distortion optimal packetization of embedded bitstreams into independent source packets

This paper addresses the rate-distortion (R-D) optimal packetization (RDOP) of embedded bitstreams into independent source packets, in order to limit error propagation in transmission of images over packet noisy channels. The input embedded stream is assumed to be an interleaving of K independently decodable basic streams. To form independent source packets, the set of basic streams is partitioned into N groups. The streams within each group are then interleaved to generate a source packet. Error/erasure protection may be further applied along/across source packets, to produce the channel packets to be transmitted. The RDOP problem previously formulated by Wu et at. has the goal of finding the partitioning that minimizes the distortion when all source packets are decoded. We extend the problem formulation such that to also include the minimization of the expected distortion for general transmission scenarios that may apply uneven erasure/ error protection. Further, we show that the dynamic programming (DP) algorithm of Wu et al. can be extended to solve the general RDOP problem. The main contribution of this paper is a fast divide-and-conquer algorithm (D&C) to find the globally optimal solution, under the assumption that all basic streams have convex R-D curves. Instrumental in obtaining the fast solution is our result which proves that the problem can be formulated as a series of matrix search problems in totally monotone matrices. The proposed D&C reduces the running time from O(K(2)LN) where L is the size of each packet achieved by the DP solution to O(NKL log K). Experiments on SPIHT coded images demonstrate that the speedup is significant in practice.     

Investigation of carbon nanofibers as support for bioactive substances

In this paper we have studied the adsorption properties of various bio-active systems onto the surface of carbon nanofibers (CNF) synthesized by chemical vapor deposition (CVD). Amino acids (alanine, aspartic acid, glutamic acid) and glucose oxidase (GOx) were adsorbed on CNF and the results were compared with those obtained when activated carbon (AC) was used as support. CNF and AC properties (hydrophilic or hydrophobic properties) were characterized by the pH value, the concentration of acidic/basic sites and by naphthalene adsorption. CNF with immobilized GOx was additionally investigated as a highly sensitive glucose biosensor. An amperometric method was used in an original manner to detect the changes in the specific activity of GOx, immobilized longer time on CNF. The method demonstrates that not the whole enzyme adsorbed onto CNF can catalyze the oxidation of glucose from the solution.     

An experimental study on the effect of hydrogen enrichment on diesel fueled HCCI combustion

This paper experimentally investigates the influence of hydrogen enrichment on the combustion and emission characteristics of a diesel HCCI engine using a modified Cooperative Fuel Research (CFR) engine. Three fuels, n-heptane and two middle distillates with cetane numbers of 46.6 and 36.6, are studied.The results show that hydrogen enrichment retards the combustion phasing and reduces the combustion duration of a diesel HCCI engine. Besides, hydrogen enrichment increases the power output and fuel conversion efficiency, and improves the combustion stability. However, hydrogen enrichment may narrow the operational compression ratio range and increase the knocking tendency. Both the overall indicated specific CO emissions (isCO) and CO emissions per unit burned diesel fuel mass are reduced by hydrogen enrichment. Although hydrogen enrichment decreases the overall indicated specific unburned hydrocarbon emissions (isHC), it does not significantly affect the HC emissions per unit burned diesel fuel mass.     

Integrating Ground-based Observations and Radar Data Into Gridding Sub-daily Precipitation

A new and general approach is proposed for interpolating 6-h precipitation series over large spatial areas. The outputs are useful for distributed hydrological modelling and studies of flooding. We apply our approach to large-scale data, measured between 2014 and 2016 at 159 weather stations network of Meteo Romania, using weather radar information and local topography as ancillary data. Novelty of our approach is in systematic development of a statistical model underlying the interpolation. Seven methods have been tested for the interpolation of the 6-h precipitation measurements: four regression methods (linear regression via ordinary least squares (OLS), with and without logarithmic transformation, and two models of generalized additive model (GAM) class, with logarithmic and identity links), and three regression-kriging models (one uses semivariogram fitted separately every 6-h, based on the residuals of the GAM with identity links models, and other two with pooled semivariograms, based on the OLS and GAM with identity links models). The prediction accuracy of the spatial interpolation methods was evaluated on a part of the dataset not used in the model-fitting stage. Due to the good results in interpolating sub-daily precipitation, normal general additive model with identity link followed with kriging of residuals with kriging parameters estimated from pooled semivariograms was applied to construct the final 6-h precipitation maps (PRK-NGAM). The final results of this work are the 6-h precipitation gridded datasets available in high spatial resolution (1000 m?×?1000 m), together with their estimated accuracy.

     

Some aspects on radiation protection in conventional and digital radiology in Romania

Since 1965, medical radiation exposure in the population of Romania has been evaluated by the Network of Radiation Hygiene Laboratories of the Ministry of Public Health, including 23 laboratories throughout the whole country; the network is co-ordinated by the Institute of Public Health Bucharest. In Romania, for a population of 22.5 million inhabitants, 465 X-ray examinations were reported during the last survey, the most frequent being chest examination. There was no specific reference to digital radiology. Digital radiology has been introduced only recently in Romania, and only some rough data on the situation can be presented. Siemens AG is now present in Romania with 23 installations, type SIEREGRAPH CF and AXIOM ICONOS. A digital image intensifier technique is used only for fluoroscopy, and radiography is performed using a conventional film/screen combination. The company Philips has nine installations for angiography, model INTEGRIS, and uses a computed radiography technique. Several direct digital radiography MULTISYSTEM SWISSRAY installations (about 40 units) are also available for adult and paediatric examinations. The Council Directive 97/43/EURATOM on health protection of individuals against dangers of ionising radiation in relation to medical exposure was fully transformed into Romanian legislation in 2002.     

POS3POLY—a MATLAB preprocessor for optimization with positive polynomials

Positive polynomials, relaxed to sum-of-squares in the multivariate case, are a powerful instrument having applications in signal processing, control and other engineering fields. Hence, appeared the need of a library which can work with positive polynomials as variables in a convex optimization problem. We present here the POS3POLY library, which transforms polynomial positivity into positive semidefinite constraints, thus enabling the user to solve such problems without the need of knowing the parameterization for each type of polynomial. POS3POLY is able to handle three types of polynomials: trigonometric, real and hybrid. The positivity of the polynomials can be global or only on a semialgebraic domain. POS3POLY allows also to define Bounded Real Lemma constraints. The library is written in MATLAB and uses SeDuMi for solving the convex optimization problems. POS3POLY can also work inside CVX. To show the usage of our library we give several examples of 2-D FIR filter design.