Application of pulse detonation technology for boiler slag removal

Pulse detonation technology for removing slag and fouling deposits in coal-fired utility power plant boilers offers great potential. This technology offers a potentially convenient, inexpensive, yet efficient way for on-line slag removal. This paper presents a feasibility study that includes both Computational Fluid Dynamics (CFD) simulations and laboratory experiments. CFD simulations provided visual and quantitative data to study the potential mechanisms for removal of slag. Mechanisms included direct impact, flow scrubbing, wave reflection and negative velocity impact on the back side of the tubes. Several experiments were carried out to verify the potential of the pulse detonation technology. Experiments were done using a pulse detonation engine and heat exchanger tubes with different types of slag placed in different orientations on the tubes. Tubes were placed at various distances from the detonation tube and in different configurations. The results present a strong case for the application of this technology for online slag removal. It is especially effective for removal of slag on the back sides of the tubes where other traditional methods are not very successful. A preliminary cost analysis indicated that the technology can be paid for within the first year itself and provide substantial savings in the subsequent years.     

Physico-mechanical properties of chemically treated coir reinforced polypropylene composites

The physico-mechanical properties of coir reinforced polypropylene (PP) composites been investigated. In order to attain improved mechanical properties of the composites coir was chemically treated with o-hydroxybenzene diazonium salt. Both raw and treated coir samples were utilized for the fabrication of the composites. The mechanical properties of the composites prepared from chemically treated coir are found to be much better compared to those of untreated ones. Tensile strengths of the composites of both raw and chemically treated coir-PP composites showed a decreasing trend with increasing filler content. However, the values for the chemically treated coir-PP composites at all mixing ratios are found to be higher than that of neat PP. The surface morphologies of the fractured surfaces of the composites were recorded using scanning electron microscopy (SEM) to gain information about the fiber–matrix interfacial adhesion in the composites.     

Some comments on frequently used multiple endpoint adjustment methods in clinical trials

Confirmatory clinical trials often classify clinical response variables into primary and secondary endpoints. The presence of two or more primary endpoints in a clinical trial usually means that some adjustments of the observed p-values for multiplicity of tests may be required for the control of the type I error rate. In this paper, we discuss statistical concerns associated with some commonly used multiple endpoint adjustment procedures. We also present limited Monte Carlo simulation results to demonstrate the performance of selected p-value-based methods in protecting the type I error rate.     

Incoherent transport in NEMO5: realistic and efficient scattering on phonons

In this work, the coherent and incoherent transport simulation capabilities of the multipurpose nanodevice simulation tool NEMO5 are presented and applied on transport in tunneling field-effect transistors. The comparison with experimental resistivity data confirms the validity of NEMO5’s phonon-scattering models. Common pitfalls of numerical implementations and the applicability of common approximations of scattering self-energies are discussed. The impact of phonon-assisted tunneling on the performance of TFETs is exemplified with a concrete Si nanowire device. The communication-efficient implementation of self-energies in NEMO5 is demonstrated with a scaling comparison of self-energies solved with blocking and nonblocking MPI-communication.     

On the quality of VoIP with DCCP for satellite communications

We present experimental results for the performance of selected voice codecs using Datagram Congestion Control Protocol (DCCP) with CCID4 congestion control over a satellite link. We evaluate the performance of both constant and variable data rate speech codecs for a number of simultaneous calls using the ITU E‐model. We analyse the sources of packet losses and additionally analyse the effect of jitter, which is one of the crucial parameters contributing to Voice over IP (VoIP) quality and has, to the best of our knowledge, not been considered previously in the published DCCP performance results. We propose modifications to the CCID4 algorithm and demonstrate how these improve the VoIP performance, without the need for additional link information other than what is already monitored by CCID4. We also demonstrate the fairness of the proposed modifications to other flows. Although the recently adopted changes to TCP‐Friendly Rate Control specification alleviate some of the performance issues for VoIP on satellite links, we argue that the characteristics of commercial satellite links necessitate consideration of further improvements. We identify the additional benefit of DCCP when used in VoIP admission control mechanisms and draw conclusions about the advantages and disadvantages of the proposed DCCP/CCID4 congestion control mechanism for use with VoIP applications. Copyright © 2012 John Wiley & Sons, Ltd.     

Preparation of Rayon Fiber-Reinforced Polypropylene Composites by Extrusion Techniques

Hybrid composites from rayon fibers (～2–5 cm size) and polypropylene (PP) were fabricated by using an extruder. Fibre content of the composite was varied from 5–30% by weight and physico-mechanical properties of the composites were measured. Surface morphology as observed by SEM showed good interface adhesion between rayon and PP matrix. Furthermore inclusion of rayon (up to 15% fiber inclusion) in the composite increased tensile, bending and hardness properties. As the fiber content in the composite increased more than 15%, physico-mechanical properties decreased due to the decrease of fiber matrix adhesion. The change of tensile properties due to environmental aging was carried out by keeping the composite under soil for 1 month and tensile properties were measured periodically. The aging result suggests that composites retained about 75% of its original tensile and bending strength even after 1 month soil burial. The modified fibers were also used for the study. As such the fibers were treated with vinyl-trimethyoxysilane and methanol solution and irradiated under UV before being used with PP in extruder. The results showed retardation of the physico-mechanical properties for composites obtained from irradiated rayon fibers than the composites fabricated from non irradiated rayon fibers.     

Scalable Nanowire Photonic Crystals: Molding the Light Emission of InGaN

To date, there have been no efficient semiconductor light emitters operating in the green and amber wavelengths. This study reports on the synthesis of InGaN nanowire photonic crystals, including dot‐in‐nanowires, nanotriangles, and nanorectangles with precisely controlled size, spacing, and morphology, and further demonstrates that bottom‐up InGaN photonic crystals can exhibit highly efficient and stable emission. The formation of stable and scalable band edge modes in defect‐free InGaN nanowire photonic crystals is directly measured by cathodoluminescence studies. The luminescence emission, in terms of both the peak position (λ ≈ 505 nm) and spectral linewidths (full‐width‐half‐maximum ≈ 12 nm), remains virtually invariant in the temperature range of 5–300 K and under excitation densities of 29 W cm^?2 to 17.5 kW cm^?2. To the best of our knowledge, this is the first demonstration of the absence of Varshni and quantum‐confined Stark effects in wurtzite InGaN light emitters—factors that contribute significantly to the efficiency droop and device instability under high‐power operation. Such distinct emission properties of InGaN photonic crystals stem directly from the strong Purcell effect, due to efficient coupling of the spontaneous emission to the highly stable and scalable band‐edge modes of InGaN photonic crystals, and are ideally suited for uncooled, high‐efficiency light‐emitting‐diode operation.     

Lipid metabolic interrelationships and phospholipase activity in gustatory epithelium ofictalurus punctatus in vitro

The catfish,Ictalurus punctatus, is an important model for studying the biochemical mechanisms of taste at the peripheral level. The type, amount and metabolic activity of the lipids within this tissue play important roles in taste transduction by forming the matrix in which the receptors for taste stimuli are imbedded and by acting as precursors to second messengers. The metabolic interconversions that occur among the lipids on the taste organ (barbels) of this animal are reported here. When sodium [³²P]phosphate was incubated with minced pieces of epithelium from the taste organ ofI. punctatus, phospholipids became labeled. Maximal incorporation occurred near 20 min for lysophosphatidylcholines (LPC),phosphatidylcholines (PC) and phosphatidylinositols (PI). The phosphatidylethanolamines (PE) and phosphatidylserines (PS) became labeled more slowly. The label in LPC and PC declined from 20 min to 120 min, while that of the other fractions increased or was stable over the 20–120 min time period. Upon addition of 1,2-di-[1′-¹⁴C]palmitoyl-sn-glycero-3-phosphocholine to the medium,¹⁴C was found within minutes in all of the phospholipids assayed. The amount of label incorporated increased with time, with maximum labeling for all phospholipids occurring at 15 min. However,¹⁴C appeared predominantly first (by 5 min) in a neutral lipid fraction (fraction AG, consisting of free fatty acids, mono- and diglycerides, triglycerides and methyl esters), then declined rapidly as the phospholipids gradually incorporated more label. Within minutes of addition of 1-[1′-¹⁴C]palmitoyl-sn-glycero-3-phosphocholine (lysophosphatidylcholine) the¹⁴C-label was detected in the neutral lipid fraction AG, then in the PC fraction, and later in the other phospholipids. The PC fraction was maximally labeled by 40 min. Using the appropriate radiolabeled substrates, lysophosphatidylcholine phospholipase A₁ and phosphatidylcholine phospholipase D activities were detected in this tissue. Very low activity of a phosphatidylcholine phospholipase A₂ was observed. The experiments indicate that there are active and rapid exchange, degradation, synthesis and scavenger pathways of phospholipids in the taste organ of this animal, and suggest that phospholipases A₁ and D-type activities are primarily responsible for the rapid breakdown of LPC and PC.