Design of serial concatenated MSK schemes based on density evolution

We consider the design of convolutional codes and low density parity check (LDPC) codes with minimum-shift keying (MSK) when the receiver employs iterative decoding and demodulation. The main idea proposed is the design of coded schemes that are well matched to the iterative decoding algorithm being used rather than to hypothetical maximum-likelihood decoding. We first show that the design is crucially dependent on whether the continuous phase encoder (CPE) is realized in recursive form or in nonrecursive form. We then consider the design of convolutionally coded systems and low density parity check codes with MSK to obtain near-capacity performance. With convolutional codes, we show that it is possible to improve the performance significantly by using a mixture of recursive and nonrecursive realizations for the CPE. For low density parity check codes, we show that codes designed for binary phase shift keying are optimal for MSK only if the nonrecursive realization is used; for the recursive realization, we design new LDPC codes based on the concept of density evolution. We show that these codes outperform the best known codes for MSK and have lower decoding complexity.     

RFID behavior study in enclosed marine container for real time temperature tracking

The performance of radio waves in open environments has been studied for years. In contrast, the behavior of Radio Frequency Identification (RFID) inside metal enclosed areas is not yet understood. This research project focuses on the 3-D mapping of RFID signal strength inside a 12 m refrigerated marine container instrumented with three different types of radio frequency (RF) emitters: 915 MHz reader; 2.45 GHz reader and 433 MHz RF transmitter. The main goal is to find a frequency/configuration that would allow real time reading of the temperature in a shipment of perishable products using RFID. Only one frequency and one antenna were used at a time. The RF transmitter antenna was mounted at two different places inside the container; at the top of the front wall (facing back) and on the ceiling in the middle of the container (facing down). The signal strength was acquired by a spectrum analyzer and its antenna was mounted on a small electric cart inside the container. The cart was programmed to move along the length of the container and stop repeatedly, allowing three automated measures per position. All data were analyzed in terms of power level and attenuation. The maps showed that the RFID antenna positioned at the front of the container delivered slightly better results than the one in the middle of the ceiling. The results showed a significantly higher performance at the 433 MHz level. This article was presented at Food Processing Automation Conference, American Society of Agricultural and Biological Engineering (ASABE), Providence, RI, June 28–29 2008.     

Bacterial and fungal microbiota of mould-ripened cheese produced in Konya

Bacterial and fungal diversities of 24 mould-ripened cheeses originating from Konya-Türkiye were examined by metagenomic analysis. Firmicutes phylum, Enterococcus, Clostridium sensu stricto and Lactobacillus (Levilactobacillus) genera were the dominant bacteria. Ascomycota phylum and Penicillium and Pichia genera and Penicillium roqueforti and Pichia membranifaciens species were dominant fungi. Enterococcus faecium (n = 30) and Enterococcus faecalis (n = 6) were identified, and all strains were susceptible to penicillin, ampicillin, vancomycin, teicoplanin, chloramphenicol and linezolid. The highest resistance (n = 14) was against rifampin. Tetracycline resistance was determined in two strains. Biofilm-forming ability was found in nine E. faecium and 1 E. faecalis. E. faecium strains revealed 40–88.9%, and E. faecalis showed 59.2–100% homology by pulsed field gel electrophoresis.     

An alternate line erasure and readout (ALER) method for implementing slot-scan imaging technique with a flat-panel detector--initial experiences

This paper describes and demonstrates an electronic collimation method, referred to as the alternate line erasure and readout (ALER) technique, for implementing slot-scan digital radiography technique with an amorphous silicon (a-Si) thin-film transistor (TFT) array based flat-panel detector. An amorphus selenium (a-Se) flat-panel detector was modified to implement the ALER technique for slot-scan imaging. A stepping-motor driven fore-collimator was mounted in front of an X-ray tube to generate a scanning X-ray fan beam. The scanning speed and magnification were adjusted to synchronize the fan beam motion with the image line readout rate. The image lines on the leading and trailing edges of the fan beam were tracked and alternately reset and read out, respectively. The former operation resulted in the erasure of the scatter signals accumulated in the leading edge image line prior to the arrival of the fan beam. The latter operation resulted in the acquisition of fan beam exposure data integrated in the trailing edge image line right after the fan beam passed. To demonstrate the scatter rejection capability of this technique, an anthropomorphic chest phantom was placed in PA position and scanned at a speed of 576 lines (8.0 cm)/s at 117 kVp and 32 mA. A tungsten bar is placed at the entrance side of the chest phantom to measure the scatter-to-primary ratio (SPR), scatter reduction factor (SRF), and contrast-to-noise ratio degradation factor (CNRDF) in the slot-scan images to evaluate the effectiveness of scatter rejection and the resultant improvement of image quality. SPR and CNRDF in the open-field images were also measured and used as the reference for comparison. A scatter reduction by 86.4 to 95.4% across lower lung and heart regions has been observed with slot-scan imaging. The CNRs have been found to be improved by a factor of 2 in the mediastinum areas over the open-field image as well.     

Injectable solid hydrogel: mechanism of shear-thinning and immediate recovery of injectable β-hairpin peptide hydrogels

β-Hairpin peptide-based hydrogels are a class of injectable hydrogel solids with significant potential use in injectable therapies. β-hairpin peptide hydrogels can be injected as preformed solids, because the solid gel can shear-thin and consequently flow under a proper shear stress but immediately recover back into a solid on removal of the stress. In this work, hydrogel behavior during and after flow was studied in order to facilitate fundamental understanding of how the gels flow during shear-thinning and how they quickly recover mechanically and morphologically relative to their original, pre-flow properties. While all studied β-hairpin hydrogels shear-thin and recover, the duration of shear and the strain rate affected both the gel stiffness immediately recovered after flow and the ultimate stiffness obtained after complete rehealing of the gel. Results of structural analysis during flow were related to bulk rheological behavior and indicated gel network fracture into large (>200 nm) hydrogel domains during flow. After cessation of flow the large hydrogel domains are immediately percolated which immediately reforms the solid hydrogel. The underlying mechanisms of the gel shear-thinning and healing processes are discussed relative to other shear-responsive networks like colloidal gels and micellar solutions.     

The relationship between crystal growth behaviour and constitution in the systems LiF-LuF3, LiF-ErF3 and LiF-YF3

The crystal growth behaviour of LiRF₄-type compounds in the systems LiF-LuF₃, LiF-ErF₃ and LiF-YF₃, have been related to the constitution of the respective systems. Crystal growth, differential thermal analysis (DTA) and microstructural studies indicate that the phases Li Lu F₄ and LiErF₄are clearly congruent in nature which is in agreement with previous work on these compounds. Corresponding studies for the compound LiYF₄ are consistent with this phase being either just congruent or just syntectic (but definitely not peritectic) in character, its constitutional behaviour depending critically on the level of contamination.     

Multilevel coded CPFSK systems for AWGN and fading channels

In this paper, we introduce multilevel coded continuous-phase frequency-shift keying (CPFSK) systems for both additive white Gaussian noise and fading channels based on multilevel coding and multistage decoding techniques. These schemes are designed under the constraint M⩾2P for M-ary CPFSK with modulation index J/P. In order to maintain the phase continuity property after multilevel coding, we use some specific set partitioning rules. We construct examples to show that the proposed systems outperform the corresponding conventional one-level schemes. For the fading case, we consider an ideal fading channel where adjacent fading symbols are assumed to be independent and a correlated fading channel where bit interleavers are needed at each coding level. The computer simulation results show that the proposed systems have bit-error performance and decoder complexity advantages over the corresponding reference codes taken from the literature. It is also shown that there is only a slight degradation on the bit-error performance for correlated fading, compared to the ideal fading case     

Joint Relay and Antenna Selection in MIMO PLNC Inter-vehicular Communication Systems over Cascaded Fading Channels

We investigate the joint relay and antenna selection performance in a multiple input multiple output (MIMO) Vehicle-to-Vehicle (V2V) communication system employing physical layer network coding (PLNC) with amplify-and-forward (AF) scheme at the relay antenna. Analytic results are derived under the cascaded Nakagami-m fading channel model assumption, which covers cascaded Rayleigh and conventional cellular channel models as well. We evaluate the performance of the system in terms of joint outage probability of sources and derive closed-form expressions for lower and upper bounds while an exact expression is found as a single integral form. Besides, the asymptotic diversity order is analyzed and quantified as a function of number of relays and antennas installed on the source and relay vehicles, and channel parameters. Finally, we verify the analytic derivations by computer simulations. Our results show that the outage probability performance decreases with the increasing cascading degrees of the channels but joint relay and antenna selection enhances the performance of the system superbly with the increasing number of relays and antennas. Also it is shown throughout all the simulation results, the lower bound for the joint outage probability seems to consistently be well tight for large SNR. Therefore it can be used for practical design of inter-vehicular communication systems which contain multiple relays and antennas.     

Serial concatenated coding scheme with minimum shift keying

A novel serially concatenated coding scheme for use with minimum shift keying (MSK) is proposed. The novelty is to use a mixture of recursive and non-recursive realisations for the MSK modulator. It is shown that this improves the performance of iterative demodulation and decoding of convolutionally encoded MSK signals with a slight decrease in the decoder complexity     

Magnetic susceptibility of polycrystalline Pr between 4 and 50 K

Measurements are reported on the magnetic susceptibility of polycrystalline Pr in the temperature range of 4–50 K in various magnetic fields. The susceptibility shows an anomaly at 23 K which reflects the antiferromagnetic ordering of the hexagonal sites. An anomaly is also observed at 33 K which is thought to arise from thec-axis susceptibility maximum, earlier observed in single crystals. The exchange interaction between Pr ions is calculated to be ?0.5 meV, showing that the interaction is antiferromagnetic. Using this value in the RKKY interaction scheme, we find thes-f coupling constant to be 0.3 eV, which agrees with other determinations.