Natural convection and radiation heat transfer in a vertical porous layer with a hexagonal honeycomb core (Part 2: heat transfer experiment)

Combined natural convection and radiation heat transfer characteristics in a vertical porous layer with a hexagonal honeycomb core were investigated experimentally. The temperature distributions on the honeycomb core wall and the combined heat transfer rates through the porous layer were measured. The measurements of the heat transfer were accomplished using the guarded hot plate method. The honeycomb core wall was made of paper and large-mesh foamed resins were inserted into the honeycomb enclosures. The measurements were performed by varying the radiation parameters between 0.5 and 0.65, varying the temperature ratios between 0.01 and 0.1, and varying the Darcy-Rayleigh numbers between 5 and 80, and for a fixed aspect ratio H/L = 1. The experimental results for Nusselt numbers agreed well with our available numerical results. © 1999 Scripta Technica, Heat Trans Asian Res, 28(4): 295–306, 1999     

FIRE RESISTANCE CHARACTERISTICS OF MATERIALS WITH POLYMER GELS WHICH ABSORB AQUEOUS SOLUTION OF CALCIUM CHLORIDE

It is well known that moist fire protection materials show good fire resistance characteristics. For this reason, these materials are usually made of mixtures of perlite-mortar and high-water-content materials such as silica gels or moist perlites. The latent heat of water plays an important role in the resistance of heat propagation in these materials. A superabsorbent polymer gel that absorbs calcium chloride solution contains much water, and it is one of these high-water-content materials. In this study, numerical simulations of fire resistance tests were conducted for materials of different mixing ratio of perlite-mortar and the super absorbent polymer gel to investigate the effect of the mixing ratio on the fire resistance characteristics. The effective thermal conductivity and the water content of the materials were measured and those values were used for computations. One of the test materials shows excellent fire resistance characteristics, and its fire resistance time at 60 mm thick is about 300 min. The relations of thermal properties and composition of the test material and the effects of mixing ratio of the gels and the perlite-mortar on the fire resistance characteristics are discussed.     

Spouting Enhancement by Addition of Small Quantities of Liquid to Gas‐Spouted Beds

The addition of liquid water to beds of polystyrene particles exceeding 3 mm in diameter enhanced spouting by causing a decrease in the minimum spouting velocity. While the degree of enhancement is quantitatively comparable to what we reported previously for fluidized beds of large light hydrophobic particles, the mechanism is quite different. Enhancement of spouting takes place because the liquid congregates at the spout‐annulus interface, forming an effective nearly‐impermeable draft tube which then increases the velocity of the gas up the spout.     

Novel ion conductive matrix via dehydrocoupling polymerization of imidazolium-type ionic liquid and lithium 9-borabicyclo[3,3,1]nonane hydride

Summary An ion conductive zwitterionic polymer electrolyte containing borate units was prepared. The polymer was synthesized via dehydrocoupling of lithium 9-borabicyclo[3,3,1]nonane hydride (lithium 9-BBN hydride) with 1,3-dihydroxyethylimidazolium bromide and subsequent anion exchange reaction using lithium bis(trifluoromethylsulfonyl)imide (LiTFSI). The obtained polymer showed the ionic conductivity of 3.4×10^-6 Scm^-1 at 50 °C in spite of relatively high glass transition temperature (-6 °C).     

Poiseuille Number Correlations for Gas Slip Flow in Micro-Tubes

Fundamental research in fluid flow characteristics in micro-tubes are required for designing microfluidic systems. In this study, Poiseuille number, the product of friction factor and Reynolds number (f · Re) for quasi-fully developed micro-tube flows, was obtained for slip flow regime. The numerical methodology was based on the Arbitrary-Lagrangian-Eulerian (ALE) method and the uncertainties of the results were assessed based on the grid convergence index (GCI). The numerical model was validated with the available experimental and numerical results. The compressible momentum and energy equations were solved for a wide range of Reynolds and Mach numbers with two thermal boundary conditions: constant wall temperature (CWT), and constant heat flux (CHF), respectively. The slip boundary conditions and their numerical implementation are appropriately documented. The tube diameter ranged from 3 to 10 μm and the tube aspect ratio was 200. The stagnation pressure was chosen in such a way that the exit Mach number ranged from 0.1–1.0. The outlet pressure was fixed at the atmospheric condition. It was found that for the case of compressible and slip flows, f · Re correlations are functions of the Mach and Knudsen numbers, and are different from the values obtained from the expression, 64/(1 + 8 Kn), available for the incompressible slip flow regime. The f · Re correlations obtained here are applicable to both no-slip and slip conditions, and for both incompressible and compressible flows. The results are in excellent agreement with the available experimental data.     

Simulation of Thermal Conductivity of Nanofluids Using Dissipative Particle Dynamics

The effective thermal conductivity of Al₂O₃/water and CuO/water nanofluids were modeled by numerically solving steady heat flow in one-dimensional microchannels. This was accomplished by using energy conserving dissipative particle dynamics (DPDe).The effects of the interfacial thermal resistance and the Brownian motion of nanoparticles were incorporated in the model by modifying the conductive interaction parameter in the energy equation. The results were presented in the form of the thermal conductivity of nanofluids as functions of particle volume fraction and temperature, and were compared with the available experimental and analytical results. The present model agreed well with the experimental results for Al₂O₃/water nanofluid, whilethere were discrepancies between the model and the results for CuO/water nanofluid.     

Clioquinol Decreases Levels of Phosphorylated,Truncated, and Oligomerized Tau Protein

The neuropathological hallmarks of Alzheimer’s disease (AD) are senile plaques (SPs), which are composed of amyloid β protein (Aβ), and neurofibrillary tangles (NFTs), which consist of highly phosphorylated tau protein. As bio-metal imbalance may be involved in the formation of NFT and SPs, metal regulation may be a direction for AD treatment. Clioquinol (CQ) is a metal-protein attenuating compound with mild chelating effects for Zn²⁺ and Cu²⁺, and CQ can not only detach metals from SPs, but also decrease amyloid aggregation in the brain. Previous studies suggested that Cu²⁺ induces the hyperphosphorylation of tau. However, the effects of CQ on tau were not fully explored. To examine the effects of CQ on tau metabolism, we used a human neuroblastoma cell line, M1C cells, which express wild-type tau protein (4R0N) via tetracycline-off (TetOff) induction. In a morphological study and ATP assay, up to 10 μM CQ had no effect on cell viability; however, 100 μM CQ had cytotoxic effects. CQ decreased accumulation of Cu⁺ in the M1C cells (39.4% of the control), and both total and phosphorylated tau protein. It also decreased the activity of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK) (37.3% and 60.7% levels of the control, respectively), which are tau kinases. Of note, activation of protein phosphatase 2A (PP2A), which is a tau phosphatase, was also observed after CQ treatment. Fractionation experiments demonstrated a reduction of oligomeric tau in the tris insoluble, sarkosyl soluble fraction by CQ treatment. CQ also decreased caspase-cleaved tau, which accelerated the aggregation of tau protein. CQ activated autophagy and proteasome pathways, which are considered important for the degradation of tau protein. Although further studies are needed to elucidate the mechanisms responsible for the effects of CQ on tau, CQ may shed light on possible AD therapeutics.     

The influence of forest management on landscape structure in the cool-temperate forest region of central Japan

Comprehension of historical changes in landscape and forest management will provide valuable insights into current ecosystems and biodiversity and will support future management decisions and conservation strategies. This study clarified changes in the forest landscape of the cool-temperate forest region of central Japan from 1947 to 1997. We used a geographic information system to reconstruct past forest landscapes at four times (1947, 1962, 1975, and 1997) based on interpretation of aerial photographs and landscape metrics calculated using the FRAGSTATS software for spatial pattern analysis. Our results showed that secondary forests, the dominant land use in 1947, decreased greatly in area and became more fragmented, whereas coniferous plantations, which occupied approximately 20% of the total land area in 1947, became the dominant land use (almost 40% of the total land) by 1997. The young coniferous plantations have been established at increasing elevations over time and were mainly created by conversion of secondary forest until 1975. The number of young coniferous plantations and their patch spacing depended on the type of forest management. In the study area, landscape structure changed in response to changes in management of national forests, especially the expansion of afforestation in the 1950s and 1960s and changes in harvesting systems.     

Polymer electrolyte membranes derived from novel fluorine-containing poly(arylene ether ketone)s by controlled post-sulfonation

Precise assignment with ¹H, ¹³C and some two dimensional NMR measurements showed that sulfonation reaction by concentrated sulfuric acid at 30 °C of fluorine-containing poly(arylene ether ketone) copolymers derived from 4,4′-bis(2,4,5,6-pentafluorobenzoyl)diphenyl ether (BPDE) and 9,9-bis(4-hydroxypehnyl)fluorene (HF) and 2,2-bis(4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane (6FBA) yielded quantitative introduction of sulfonic groups onto 2- and 7-positions of fluorene ring in HF unit. A series of sulfonated poly(arylene ether ketone)s with different ion exchange capacity was prepared by using this method with different compositions of HF and 6FBA, and membranes obtained from these polymers were characterized by TGA, moisture and water uptake, proton conductivity, methanol permeability, and Fenton testing. These membranes showed sufficient thermal stability, high proton conductivity at high humidified condition for PEFC and good balance in proton conductivity in water and methanol permeability for DMFC. On the other hand, they showed relatively high swelling by water probably due to weak intermolecular interaction caused by the existence of fluorine atoms in the polymer structure.