Frequency-Dependent Attenuation Effects in Pulsed Doppler Ultrasound: Experimental Results

The quantitative capability of pulsed Doppler ultrasound in clinical practice is limited by the effects of frequency-dependent attenuation of ultrasound in tissue, as well as several other spectral-broadening mechanisms which distort the Doppler spectrum of an ultrasonic echo. In this communication, we present results of in vitro experiments which demonstrate the magnitude of the errors expected in clinical measurements of blood flow parameters when frequency-dependent attenuation Of ultrasound in biological tissue is ignored. It is shown that errors as large as 15 percent may occur in Doppler measurements of blood flow velocity through 7 cm of intervening tissue. A comparison is also made between experimental results and a theoretical model which includes the effects of scattering and attenuation.     

On the limit theory of the Gaussian SQMLE in the EGARCH(1,1) model

We derive the limit theory of the Gaussian stable quasi maximum likelihood estimator for the stationary EGARCH(1,1) model when the squared innovation process has marginals with regularly varying tails. We derive regularly varying rates and limiting stable distributions. We perform Monte Carlo experiments to assess the extent of the parameter space corresponding to the invertibility condition, and the quality of the asymptotic approximation.     

An EWMA signed ranks control chart with reliable run length performances

During the design phase of a control chart, the determination of its exact run length properties plays a vital role for its optimal operation. Markov chain or integral equation methods have been extensively applied in the design phase of conventional control charts. However, for distribution-free schemes, due to the discrete nature of the statistics being used (such as the sign or the Wilcoxon signed rank statistics, for instance), it is impossible to accurately compute their run length properties. In this work, a modified distribution-free phase II exponentially weighted moving average (EWMA)-type chart based on the Wilcoxon signed rank statistic is considered and its exact run length properties are discussed. A continuous transformation of the Wilcoxon signed rank statistic, combined with the classical Markov chain method, is used for the determination of the average run length in the in- and out-of control cases. Moreover, its exact performance is derived without any knowledge of the distribution of sample observations. Finally, an illustrative example is provided showing the practical implementation of our proposed chart.     

Path Representation in Circuit Netlists Using Linear-Sized ZDDs with Optimal Variable Ordering

The efficient representation and manipulation of a large number of paths in a Directed Acyclic Graph (DAG) requires the usage of special data structures that may become of exponential size with respect to the size of the graph. Several methodologies targeting Electronic Design Automation problems such as timing analysis, physical design, verification and testing involve path representation and necessary manipulation. Previous works proposed an encoding using Zero-suppressed Binary Decision Diagrams (ZDDs), which has been shown experimentally to cope well when representing structural or logical paths in VLSI circuits. However, it is well known that the ordering of the variables in a ZDD highly affects its size and, therefore, the efficiency of the methodologies utilizing these data structures. In this work, we show that using a reverse topological order for the ZDD variables bounds the number of nodes in the ZDD representing structural paths to the number of edges in the DAG considered, hence, making the ZDD size linear to the DAG’s size. This result, supported here both theoretically and experimentally, is very important as it can render methodologies with questionable scalability applicable to larger industrial designs. We demonstrate the applicability of the proposed variable ordering in one such methodology which utilizes ZDDs to grade the Path Delay Fault coverage of a given test set.     

Printing highly efficient organic solar cells

The technological attraction in organic solar cells is their compatibility to printing processes. However, up to today, nearly no literature on "printed" organic solar cells have been published and the major body of the research work was done by spin coating or blading techniques. Transferring the spin-coating or doctor blading process currently used for the fabrication of bulk heterojunction solar cell to a printing process holds morphological challenges that have not been observed or reported up to today. We highlight these challenges and we show that inkjet printing of organic bulk heterojunction solar cells requires completely novel approaches and skill sets compared to the current state of the art. By adjusting the chemical properties of the poly(3-hexylthiophene) polymer donor and by using our recently developed inkjet solvent mixture, we have gained control over the nanomorphology of poly(3-hexylthiophene):fullerene blends during the printing process and report a new record power conversion efficiency of 3.5% for inkjet printed poly(3-hexylthiophene):fullerene based solar cells.     

Collapse of partially corroded or worn pipe under external pressure

This paper is concerned with the effect of internal corrosion or erosion defects on the collapse of pipelines under external pressure. Experiments are conducted on SS-304 tubes with D/t's of 21.0 and 18.7 with axially uniform grooves of several thicknesses and angular spans of 6–60°. All specimens exhibited the classical ovalization mode of collapse with the grooved side being more deformed. For groove angles between 6° and 20° the collapse pressure decreases as the angle increases but remains essentially constant for angles between 20° and 60°. The collapse pressure was found to decrease with groove depth, reducing by nearly 50% when the groove depth reached 50% of the pipe wall thickness. The experiments were simulated numerically using both the custom computer code BEPTICO as well as an axially uniform finite element model. The predictions were found to follow closely the trends of the experimental results. The three dimensionality of grooves was examined using appropriate finite element models. It was found that grooves shorter than about 8D constitute local imperfections and accurate prediction of their effect on collapse pressure requires fully 3-D modeling. By contrast, grooves 10D long or longer behave essentially as “long” grooves and can be analyzed using 2-D models.     

Reduction of Escherichia coli O157:H7 viability on leafy green vegetables by treatment with a bacteriophage mixture and trans-cinnamaldehyde

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 has been recognized as a major foodborne pathogen responsible for frequent gastroenteritis outbreaks. Phages and essential oils can be used as a natural antimicrobial method to reduce bacterial pathogens from the food supply. The objective of this study was to determine the effect of a bacteriophage cocktail, BEC8, alone and in combination with the essential oil trans-cinnameldehyde (TC) on the viability of a mixture of EHEC O157:H7 strains applied on whole baby romaine lettuce and baby spinach leaves. The EHEC O157:H7 strains used were Nal^R mutants of EK27, ATCC 43895, and 472. Exponentially growing cells from tryptic soy (TS) broth cultures were spot inoculated on leaves and dried. EHEC cells were placed at low, medium, and high inoculum levels (10⁴, 10⁵, and 10⁶ CFU/mL, respectively). Appropriate controls, BEC8 (approx. 10⁶ PFU/leaf), and TC (0.5% v/v) were applied on treated leaves. The leaves were incubated at 4, 8, 23, and 37 °C in Petri dishes with moistened filter papers. EHEC survival was determined using standard plate count on nalidixic acid (50 μg/mL) Sorbitol MacConkey agar. No survivors were detected when both leaves were treated with BEC8 or TC individually at low inoculum levels after 24 h at 23 and 37 °C. When the EHEC inoculum size increased and/or incubation temperature decreased, the efficacy of BEC8 and TC decreased. However, when the two treatments were combined, no survivors were detected after 10 min at all temperatures and inoculum levels on both leafy greens. These results indicated that the BEC8/TC combination was highly effective against EHEC on both leafy greens. This combination could potentially be used as an antimicrobial to inactivate EHEC O157:H7 and reduce their incidence in the food chain.     

Flexible organic P3HT:PCBM bulk-heterojunction modules with more than 1 year outdoor lifetime

Flexible organic solar cells and modules based on P3ht:PCBM bulk-heterojunctions were fabricated and their lifetime was investigated under laboratory and outdoor conditions. In the laboratory cells were exposed to 1 sun illumination at 65 °C in order to accelerate the degradation. The outdoor behavior of modules was investigated at the Konarka rooftop testing setup in Lowell, MA (USA). We show that these flexible polymer solar cells have a good light stability, passing 1000 h under accelerated light soaking conditions in the laboratory, and that flexible modules survived over 1 year of outdoor exposure without performance losses.     

Occupancy‐based decision support system for building management: From automation to end‐user persuasion

In this paper, an intelligent occupancy‐based, automated building control system is initially introduced, which has the capability of reducing energy consumption while respecting the occupants' comfort and actions inside building areas. Data stemming from a multisensorial network is combined with implicitly extracted information, since no direct feedback is expected by the users, towards unsupervised monitoring and control of building operation. However, due to significantly higher costs of actuating equipment and the reluctance that some end users show in accepting fully automated solutions, a new hybrid approach is conceptualized and presented; the automated decision support system is supplemented with a persuasion mechanism aimed at increasing energy savings, through raising user awareness. The persuasive methodology employs a continuous feedback mechanism in order to select the optimal incentive strategy by taking into account user success rates, in terms of requested actions, as well as available mechanisms, and daily harassment.