Heat transfer enhancement of turbulent duct flow by vortex generators attached to a large eddy break-up manipulator

An experimental study was conducted to investigate the characteristics of wall heat transfer and momentum loss for turbulent duct flow disturbed by insertion of a complicated body composed of a Large Eddy Break-Up (LEBU) plate and winglet-type vortex generators. It was found that the LEBU plate reduces the wall heat transfer in the region downstream of the insertion position and that this suppression of heat transfer could be recovered by attaching vortex generators to the LEBU plate, i.e., conspicuous heat transfer enhancement was achieved over a large streamwise distance. The spatial distribution of the heat transfer coefficient obtained shows the same features as that observed in a previous study of a flat plate turbulent boundary layer. Therefore, the flow and thermal field structure of the turbulent duct flow downstream of the inserted body should be basically the same as those in the same region of the turbulent boundary layer. The effect of a notch, open in the LEBU plate behind the vortex generator, on heat transfer and pressure drop was also examined. The notch simulates the hole of the LEBU plate to be produced in a practical application when a vortex generator is produced by punching from the original plain LEBU plate. It was found that a vortex generator with an open notch works best in augmenting the wall heat transfer and also in suppressing the increase of momentum loss. © 1999 Scripta Technica, Heat Trans Asian Res, 28(3): 189–200, 1999     

Formation of False Context Fear Memory Is Regulated by Hypothalamic Corticotropin-Releasing Factor in Mice

Traumatic events frequently produce false fear memories. We investigated the effect of hypothalamic corticotropin-releasing factor (CRF) knockdown (Hy-Crf-KD) or overexpression (Hy-CRF-OE) on contextual fear memory, as fear stress-released CRF and hypothalamic–pituitary–adrenal axis activation affects the memory system. Mice were placed in a chamber with an electric footshock as a conditioning stimulus (CS) in Context A, then exposed to a novel chamber without CS, as Context B, at 3 h (B-3h) or 24 h (B-24h). The freezing response in B-3h was intensified in the experimental mice, compared to control mice not exposed to CS, indicating that a false fear memory was formed at 3 h. The within-group freezing level at B-24h was higher than that at B-3h, indicating that false context fear memory was enhanced at B-24h. The difference in freezing levels between B-3h and B-24h in Hy-Crf-KD mice was larger than that of controls. In Hy-CRF-OE mice, the freezing level at B-3h was higher than that of control and Hy-Crf-KD mice, while the freezing level in B-24h was similar to that in B-3h. Locomotor activity before CS and freezing level during CS were similar among the groups. Therefore, we hypothesized that Hy-Crf-KD potentiates the induction of false context fear memory, while Hy-CRF-OE enhances the onset of false fear memory formation.     

Carbonization of aromatic hydrocarbons—V: Microscopic features of carbons obtained by the aid of catalysts

Microscopic observation of carbons obtained from pure aromatic hydrocarbons by the aid of carbonization catalysts was carried out to clarify the microstructure of these carbons of different features. Reflected polarized-light microscopy distinguished needle, mosaic and isotropic cokes, former two of which were produced with aluminum chloride and the last with potassium. High resolution microscopy revealed that these carbons calcined at 1250° had different degree of layered structure, corresponding to the crystallographic parameters of these samples graphitized at 2500°C. The reasons for the carbons produced with potassium to be non-graphitizable are discussed from the macro- and micro-features of the carbons.     

Modifying carbonization properties of pitches. 3. Carbonization of modified quinoline-insoluble matter from pitches

The carbonization of solubilized matter obtained from the hydrogenated and reductively alkylated quinoline-insolubles of pitches was studied to clarify the different carbonization properties shown by these materials. Dehydrogenation of hydrogenated QI started at 200 °C but continued until 400 °C, passing through a fused phase to give graphitizable carbon. In contrast, alkylated QI gave non-graphitizable carbon because it readily reverted to QI by dealkylation below 300 °C, before fusion. QI alkylated with butyl or benzyl groups was found to be nearly 80% soluble in benzene.     

Liquefaction of subbituminous coals under apparently non-hydrogenative conditions

Reactivities of several coals of different ranks have been examined in degrading extractions with aromatic solvents under apparently non-hydrogenative reaction conditions. Pyrene and A240 pitch liquefied the fusible coals in high yields and the slightly-fusible coals in moderate yields, indicating the importance of fusibility in such liquefaction processes. A240-LS pitch is a powerful solvent for slightly-fusible coals. Considerable amounts of pyridine- or THF-soluble fractions were produced especially with A240-LS pitch. A240 pitch is a better solvent than pyrene for some slightly-fusible coals. However, the extent of depolymerization of liquefied coal, pyridine- or THF-solubility, was definitely inferior. Yields of such fractions are higher for lower-rank coals. The mechanism of coal liquefaction under apparently non-hydrogenative conditions is discussed with emphasis on the stabilization of thermal fragments derived from the coal.     

Synthesis and chiroptical properties of helical poly(phenylacetylene) bearing optically active chiral oxazoline Pendants

The novel optically active (S)-4-benzyl-2-(ethynylphenyl)-oxazoline (BnEPhOx) was successfully prepared and polymerized using rhodium catalyst ([Rh(nbd)Cl]₂) to obtain the moderate molecular weight poly(phenylacetylene)s bearing chiral oxazoline derivatives with high yields (≥90%). The ¹H NMR spectra demonstrated that the resulting polymers had high stereoregular structures. Moreover, the poly(phenylacetylene)s bearing chiral oxazoline exhibited better thermal stability than poly(phenylacetylene). The resulting polymers showed higher absolute values of optical specific rotation than the monomer. The polymers also exhibited intense CD signal in the region of the π-π1 band of the conjugated polyacetylene backbone in chloroform solution. The results of specific rotation and CD spectroscopy indicated that all the polymers adopted higher-order structure with predominantly one-handed screw sense.In addition, the resulting polymers emitted fluorescence under UV irradiation.     

Asymmetric anionic polymerization of n-diphenyl-methylitaconimide with chiral ligand-organometal complex

Summary Asymmetric anionic polymerizations of achiral N-diphenylmethylitaconimide (DPII) were performed with chiral ligand — organometal complexes in toluene. The obtained poly(DPII)s exhibited molecular weights of 1.5 × 10³ to 6.3 × 10³ and specific rotation between +7.5 to −18.4° (THF). The chirality of polymer was significantly affected by the organometals and chiral ligands. The poly(DPII) obtained with (4S)-2,2′-(1-ethylpropylidene)bis(4-benzyl-4,5-dihydrooxazole) (Bnbox) / n-butyllithium (n-BuLi) exhibited the highest specific rotation (−18.4°). The optical activities of the poly(DPII)s were attributed to configurational chirality of the main chain more than conformational chirality, judged from NMR, circular dichroism (CD) and GPC analyses using UV and polarimetric detectors. Received: 10 January 2002/ Revised: 12 April 2002/ Accepted: 22 April 2002     

Aqueous solution properties of a silicone surfactant and its mixed surfactant systems

The aqueous solution properties of a nonionic silicone surfactant of dimethylpolysiloxane and its mixed surfactant systems were studied. It was found that the silicone surfactant has a high surface activity and forms micelles in two steps: premicelles in dilute concentrations and polymolecular micelles above 3.7 × 10⁻⁷ mol dm⁻³. In mixed systems of the silicone surfactant with anionic hydrocarbon or fluorocarbon surfactant, weak intermicellar interactions were found. They are due to electrostatic interaction between hydrophilic groups of the respective micelles. Dye solubilization measurements showed that the solubilized amount of Yellow-OB is greater than predicted by ideal systems. Hydrazo-azo tautomerism is observed in fluorocarbon-silicone surfactant systems, while Yellow-OB is solubilized only in the azo-form in the hydrocarbon-silicone surfactant system.     

Modification and laboratory evaluation of a TSI ultrafine condensation particle counter (Model 3776) for airborne measurements

A butanol-type ultrafine condensation particle counter (UCPC, Model 3776, TSI, Inc., Shoreview, MN, USA), which can achieve a 50% detection efficiency diameter (d₅₀) of 2.5 nm using a capillary-sheath structure, was modified and tested in the laboratory for airborne measurements. The aerosol flow rate through the capillary is a key factor affecting the quantification of aerosol particle number concentrations. A pressure-dependent correction factor for the aerosol flow rate was determined using a newly added mass flow meter for the sheath flow and the external calibration system. The effect of particle coincidence in the optical sensing volume was evaluated using an aerosol electrometer (AE, Model 3068B, TSI, Inc.) as a reference. An additional correction factor for the coincidence effect was derived to improve the quantification accuracy at higher concentrations. The particle detection efficiency relative to the AE was measured for mobility diameters of 3.1–50 nm and inlet absolute pressures of 101–40 kPa. The pressure dependence of the d₅₀ value, asymptotic detection efficiency, and shape of the particle detection efficiency curve is discussed, along with simple theoretical calculations for the diffusion loss of particles and the butanol saturation ratio in the condenser.

© 2017 American Association for Aerosol Science     

Aerosol-to-liquid collection: A method for making aqueous suspension of hydrophobic nanomaterial without adding dispersant

This article introduces an aerosol-based technique to make aqueous suspension of hydrophobic nanomaterial without adding dispersant. The method is intended for making a test-sample for evaluating the toxicities of nanomaterial by intra-tracheal administration. The method can wet the surface of hydrophobic nanomaterial within a few seconds. After the wetting process five to ten minutes of sonication assisted with manual stirring can fully disperse the hydrophobic nanomaterials in water. Two types of TiO₂ nanomaterial were used in this study; Tayca JMT-150IB whose surfaces are coated with negatively charged hydrophobic functional group, and P25 whose surfaces are naturally hydrophilic. Nanomaterials are aerosolized by a dry-method and become micrometer-sized agglomerates. Then supersaturated water vapor is condensed onto these airborne agglomerates by using a growth tube collector. The collected suspension (CS) of hydrophobic nanomaterial (JMT-150IB) is prepared in two steps; airborne agglomerates are collected onto a flat surface then transferred to liquid-water and subsequently sonicated for complete dispersion. This method works equally well for making the CS of hydrophilic nanomaterial. Size distribution measurements of the CS show that airborne agglomerates of TiO₂ dissociate into smaller units of agglomerates once they are captured into water, and the sizes of the agglomerates are in the nanometer to sub-micrometer range. Light scattering technique is used to show that a short sonication process can reproduce the particle number concentration of the CS after long storage.

Copyright © 2017 American Association for Aerosol Research