Thermoelectrically controlled micronozzle — A novel application for thermoelements

This paper introduces and assesses the concept of the recently invented thermoelectrically controlled micronozzle (TECMN). A generalized quasi-one-dimensional model for gas flow, which is influenced by area variation and by wall heat transfer, is considered. In order to assess the merits of wall temperature control in micronozzles, the flow in the micronozzle is solved numerically for cases of convergent wall heating, divergent wall cooling, and a combination of both. Thermal efficiency and specific impulse are affected by heat exchange through the side wall of the micronozzle. By cooling the divergent section, kinetic energy increases, thus improving thermal efficiency. The mass flow rate is decreased in all cases that include convergent section heating, thereby enhancing specific impulse. The combination of convergent section heating with divergent part cooling results in significant performance enhancement in terms of thermal efficiency and specific impulse. To determine the TECMN wall temperature profile, we developed a one-dimensional general energy model for a thermoelement (TE) subject to an electric field as well as for heat convection on the lateral surface. The energy equation is analytically solved for constant properties and for Joule heating equivalent to heat convection. The temperature profile is then imposed on the quasi-one-dimensional flow model, which is solved numerically for various mass flow rates and exit wall temperature (cold junction). As the exit section wall temperature and mass flow rate decrease, the utilization of TEs to control the temperature of micronozzle walls considerably increases the Mach number at exit.     

Genes of the transforming growth factor-beta signalling pathway are associated with pre-implantation embryonic development in cattle

One of the main factors affecting cattle fertility is pre-implantation development of the bovine embryo, which is a complex process regulated by various signal-transduction pathways. The transforming growth factor-β (TGF-β) signalling system, which is responsible for many biological processes including cell proliferation, differentiation and apoptosis, also is involved in embryo development. We hypothesized that altered expression of TGF-β genes in pre-implantation bovine embryos is associated with morphological abnormalities of these embryos. To test this hypothesis, we produced embryos in vitro and classified them at the blastocyst stage as either normally developed blastocysts or degenerates (growth-arrested embryos). The expression patterns of 25 genes from the TGF-β pathway were assessed using quantitative real time PCR. Ten genes showed differential expression between the two embryo groups, four genes displayed similar expressional profiles, and 11 genes had no detectable expression. An altered expression profile was statistically significant for 10 of the 14 expressed genes, and all were up-regulated in degenerate embryos vs. blastocysts. Furthermore, genomic association analysis of the cows from which embryos were produced revealed a significant association of ID3 and BMP4 polymorphisms--two of the most significant differentially expressed genes--with fertilization rate and blastocyst rate, respectively. Taken together, we conclude that TGF-β pathway genes, especially BMP4 and ID3 play a vital function in the regulation of pre-implantation embryo development at both embryo and maternal levels. Hence, these genes may be suitable as genetic markers for embryo development and fertility in cattle.     

Variability aware low leakage reliable SRAM cell design technique

This paper presents a technique for designing a low power SRAM cell. The cell achieves low power dissipation due to its series connected drivers driven by bitlines and read buffers which offer stack effect. The paper investigates the impact of process, voltage, and temperature (PVT) variations on standby leakage and finds appreciable improvement in power dissipation. It also estimates read/write delay, read stability, write-ability, and compares the results with that of standard 6T SRAM cell. The comparative study based on Monte Carlo simulation exhibits appreciable improvement in leakage power dissipation and other design metrics at the expense of 84% area overhead.     

Extended MULE Concept for Traffic Congestion Monitoring

Wireless Sensor Networks are being recently studied to monitor real-time traffic conditions on roads and highways. Idea of using vehicles to convey information from sensors placed alongside roads to the dedicated base stations has also been under scrutiny for some time. In this paper, we argue that a sensor placed on a vehicle instead of a fixed location can effectively sense traffic congestion on the road and report it to the already available WLAN Access Points (APs) instead of the dedicated base stations. This way, instead of deploying series of base stations to collect traffic information, congestion information can be sent over the ISM links between the vehicular sensor nodes and the WLAN APs. This paper investigates, as we call it, the Extended MULE concept by using actual experimental data obtained from the test drives across the city. Our results show that adopting this idea is effective in reporting traffic congestion on the roads.     

A link adaptation scheme for the downlink of mobile hotspot

A link adaptation (LA) scheme for the downlink of mobile hotspot, which is supported by an IEEE 802.16e or mobile WiMAX network, is proposed. The mobile WiMAX uses orthogonal frequency division multiple access (OFDMA) in its physical layer. The main function of the LA scheme is to select an appropriate burst profile, which includes a multiple input multiple output (MIMO) transmission mode, modulation technique, and coding scheme. We formulate a discrete optimization problem for the LA scheme by maximizing the throughput. An algorithm to implement the LA scheme is also proposed. Numerical results show that the proposed LA scheme exhibits good performance. Copyright © 2011 John Wiley & Sons, Ltd.     

Polyzwitterion-to-polyampholyte transition using pH-responsive cycloterpolymers of diallyldimethylammonium chloride, (N,N-diallylammonio)methanecarboxylate and sulfur dioxide

The cycloterpolymerizations of varying proportions of diallyldimethylammonium chloride (I) and N,N-Diallyl-N-carboethoxymethylammonium chloride (II) in the presence of sulfur dioxide afforded a series of cationic (+) polyelectrolytes (CPEs) (III) in excellent yields. CPEs, upon acidic hydrolysis of the ester functionalities of the repeating units of II, resulted in the formation of cationic/zwitterionic (+/±) polymers (IV). pH-responsive zwitterionic units of ammonioethanoate (NH⁺CH₂CO) (having unquenched valency of nitrogen) in IV was converted to its anionic counterparts (NCH₂CO) by treating with equivalent amount of NaOH to give cationic/anionic i.e., ampholytic (+/−) polymers (V) with a charge symmetry or asymmetry arising out of either excess of cationic or anionic centers. The transformations of III to IV to V have thus provided an opportunity to study the effects of the polyelectrolyte-to-polyzwitterion-to-polyampholyte transitions on the solution properties of these polymers. Basicity constants of the carboxylate group (NH⁺CH₂CO) in IV as well as the amine group (NCH₂CO) in V were found to be “apparent” and as such follow the modified Henderson–Hasselbalch equation. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of oscillation amplitude on velocity distributions in an oscillatory baffled column (OBC)

This paper presents a numerical study of the effect of oscillation amplitude in oscillatory baffled column (OBC) using computational fluid dynamics. The numerical work was carried out for single phase liquid flow for an unsteady 3-D model using commercial software, Fluent (2006). This work was concentrated on the effect of oscillation amplitude. Three amplitudes of 5, 10 and 15 mm with constant frequency of 1 Hz are applied. Vortex and cycle average velocities at different points are analyzed. The studies show the maximum velocity for 5 mm, 10 mm and 15 mm in an OBC are 0.11 m/s, 0.25 m/s and 0.40 m/s respectively in the first cycle of oscillation. At a constant frequency, greater oscillation amplitude displaces the liquid to a further distance and builds a larger vortex. Vortex length was 1.5 times bigger when oscillation amplitude changes from 5 mm to 10 mm and 2 times when the amplitude is triple from 5 mm. The detailed validation is presented somewhere else; this research is focused on the effect of oscillation.     

Improvement in the bonding strength of laminated composites by using air‐textured core‐and‐effect glass yarns

Delamination is the most common failure mode in laminated composites due to the reduced strength in the through‐the‐thickness direction. Air‐jet texturing was used to produce bulk and loops in the yarn, which provides more surface contact between the fibers and the resin. The development of core‐and‐effect textured glass yarns and the effect of texturing parameters were presented in the previous article. This article describes the effect of texturing on the mechanical properties including tensile properties, flexure properties, interlaminar shear strength (ILSS) and fracture toughness (Mode I) of glass laminated composites. The composites of plain and twill weave fabrics were developed from both the textured and nontextured yarns. It was observed that the tensile properties decreased and the flexure properties remained unchanged after texturing. However, significant improvement was observed in ILSS and the Mode I fracture toughness of the composites after texturing. The bulkier, loopy structure of the textured yarn provided more surface contact between the fiber and the resin and significantly improved the bonding strength. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Improving the bonding strength of laminated composites by optimizing fabric composition

Delamination is the most common failure mode in laminated composites due to the weaker strength in the through‐the‐thickness direction. Air‐jet texturing is used to produce bulk and loops in the yarn which provides more contact surface between fibers and resin. The development and characterization of core‐and‐effect textured glass yarns and the effect of texturing on the mechanical properties of laminated composites were presented in previous papers. This article describes the optimization of textured composites by varying the type and combination of constituent yarns for improving the mechanical properties. Composites with combinations of various textured yarns and non‐textured yarns were made. It was observed that the composites made from fabrics having non‐textured yarn in the warp and core‐and‐effect textured yarn in the weft had the best combination of mechanical properties. They maintained the tensile and flexure properties of composites with non‐textured yarns but had significantly higher interlaminar shear strength. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers