Studies on bulk diffusion and local diffusion of polystyrene in melt

Results of bulk viscosity (η) and local viscosity (ξ) of various molecular weights of polystyrene (PS) have been reported. In this paper the relationship between η and bulk diffusion coefficient (D_B), and that between ξ and local diffusion coeffizient (D_L) are presented. Data obtained lead to several conclusions. From the results of unperturbed dimensions and a universal constant (Φ), it was found that F. Bueche's equation D_B · η = const. is valid for polystyrenes with molecular weights over 600. Temperature and component concentration dependence of bulk diffusion coefficient for the two-component blend system may be interpreted in terms of the free volume theory. At an iso-free volume state, molecular weight dependences of bulk diffusion coefficients for both PS of narrow distribution of molecular weight and blend PS can be composed to a single curve, which is composed of two straight lines in a double logarithmic presentation with intersection at M_w = 1.78 × 10⁴ g/mol. The slopes of these two lines were ? 1.0 and ? 3.3, respectively. The product D_L · ξ was determined to be 1.10 × 10^?7 (c.g.s) for n-paraffines from the data of self-diffusion coefficient and ξ. This made it possible to determine D_L from ξ. For higher molecular weights of PS, log D_B is a linear function of log M_w while log D_L stays almost constant.     

The effects of point defects on transmission coefficients in two-dimensional piezoelectric phononic crystals

Based on finite-difference time-domain(FDTD) method,the wave propagation and localization in two-dimensional defect-containing piezoelectric phononic crystals are investigated when the mechanical-electrical coupling is taken into account.The characteristics of localized defect modes are studied,and the effects of the number and direction of defects on the defect modes and transmission coefficients are discussed.Numerical results of defect modes and transmission coefficients are presented for BaTiO3/polymer piezocomposite,and from which we can see that the number and direction of defects have pronounced effects on the defect modes and transmission coefficients.The results also show the existence of elastic wave localization in piezoelectric phononic crystals containing defects.     

Role of NADH shuttle system in glucose-induced activation of mitochondrial metabolism and insulin secretion

Glucose metabolism in glycolysis and in mitochondria is pivotal to glucose-induced insulin secretion from pancreatic beta cells. One or more factors derived from glycolysis other than pyruvate appear to be required for the generation of mitochondrial signals that lead to insulin secretion. The electrons of the glycolysis-derived reduced form of nicotinamide adenine dinucleotide (NADH) are transferred to mitochondria through the NADH shuttle system. By abolishing the NADH shuttle function, glucose-induced increases in NADH autofluorescence, mitochondrial membrane potential, and adenosine triphosphate content were reduced and glucose-induced insulin secretion was abrogated. The NADH shuttle evidently couples glycolysis with activation of mitochondrial energy metabolism to trigger insulin secretion.     

A CMOS image sensor module applied for a digital still camerautilizing the TAB on glass (TOG) bonding method

The world's smallest (105×55×20 mm) and lightest (130 g) digital still camera has been developed, in which a 330 K pixel complementary metal-oxide-semiconductor (CMOS) image sensor chip is used as an image sensor. The authors have developed a new thinner and smaller image sensor module, called tape automated bonding (TAB) on glass (TOG) module, using the anisotropic conductive paste (ACP) interconnection method. The TOG production process was established by obtaining optimum bonding conditions for both optical glass bonding and CMOS chip bonding to the TAB tape. The bonding conditions including sufficient bonding margins, were mainly studied. The TOG module obtained good imaging properties, It also has a high reliability such as thermal cycle test (-40 to +110°C/30 min, 2000 cycles) and the high temperature storage test (60°C, 90% RH, 3000 h). The stable production process was confirmed by fabricating an automatic bonding machine     

Exergy recuperative CO2 gas separation in pre-combustion capture

The integrated coal gasification combined cycle (IGCC) can achieve higher power generation efficiency than conventional pulverized coal combustion power plants. However, a CO₂ capture process prevents improving power generation efficiency of IGCC, because CO₂ separation from gas mixtures requires huge amounts of energy. Therefore, in this study, we analyzed the CO₂ separation process in the pre-combustion capture process using a process simulator (PRO/II) in the steady state, and proposed a new process using a modularity based on self-heat recuperation (SHR) technology to decrease energy consumption. Pre-combustion capture was applied in the IGCC plant, which involved coal gasification and CO-shift conversion with CO₂ capture. The results show that the energy consumption for the CO₂ separation process using SHR was decreased by two-thirds. This means that the power generation efficiency can be improved by SHR compared with conventional IGCC with a CO₂ capture process.     

A numerical investigation of evaporation characteristics of a fuel droplet suspended from a thermocouple

Numerical simulations of combined natural convection–conduction in a droplet of n-dodecane suspended from a thermocouple were carried out, taking into consideration evaporation, and the effect of thermocouple diameter on the evaporation characteristics was investigated. The calculated temperature history of the droplet is in good agreement with experimental results; both show that the rate of heating decreases with increasing thermocouple diameter. The maximum error in temperature due to the thermocouple increases linearly with increasing thermocouple diameter. Thus, in investigations involving a droplet suspended from a thermocouple, it is preferable to use a thermocouple with the smallest possible diameter.     

Development of a mathematical model for predicting water vapor mass generated in micro-explosion

This paper describes a mathematical model for predicting the mass of water vapor generated in micro-explosion. First, a single droplet experiment was carried out. A W/O (water/oil) emulsified fuel droplet suspended by a thermocouple was heated by a halogen spot heater, and micro-explosion was observed using a high-speed video camera. The progress of the coalescence of the dispersed water droplet was observed while droplet was heated, and an aggregated water droplet was formed in the oil layer. Based on the measured micro-explosion characteristics, a mathematical model for predicting water vapor mass generated in micro-explosion was proposed. The size of the aggregated water droplet just before micro-explosion was measured to verify the proposed mathematical model. Under certain assumptions, mass and energy conservation equations were applied to micro-explosion process, and an equation to calculate water vapor mass generated in micro-explosion was derived. The derived equation and some measurement results provide enough information to calculate water vapor mass generated in micro-explosion. The calculated diameter of the water droplet, which changed to vapor in micro-explosion, was compared to that of the aggregated water droplet just before micro-explosion. The calculated results roughly agreed with experimental ones, and the validity of the proposed model was verified.     

Calcium isotope separation by band chromatography using 18-crown-6-ether resin

To develop the ⁴⁸Ca enrichment process, a feasibility study on a band chromatography was made using 9 M HCl solution and crown ether resin synthesized in porous silica beads. Prior to the chromatographic experiments, distribution coefficients, Kd, of Ca²⁺ and Sr²⁺ were measured at different concentrations of these ionic species. The frontal boundary of the chromatography was made by a usual manner of the breakthrough mode of calcium feeding, and the rear boundary was made by introducing strontium as a following ion on the basis of the observed Kd values. It was confirmed that the heavy isotope ⁴⁸Ca was depleted in the rear boundary region, while ⁴⁸Ca was enriched in the front boundary region. The values of separation coefficient ε (= α – 1) in three chromatographic operations at different temperatures were observed as 2 × 10^?3 ~ 3 × 10^?3. The separation coefficients observed in the front boundary regions, where ⁴⁸Ca was enriched, agreed with those observed in the rear boundary regions, where ⁴⁰Ca was enriched.     

Improvement of piezoresistance properties of silicon carbide ceramics through co-doping of aluminum nitride and nitrogen

The piezoresistance coefficient was measured on co-doped silicon carbide ceramics. Evaluation samples of -silicon carbide ceramics were first fabricated by glass capsule HIP method using powder mixture of silicon carbide and aluminum nitride with various ratios. The resultant aluminum nitride added silicon carbide ceramics were doped with nitrogen by changing the post-HIP nitrogen gas pressure. The lattice parameter increased with the amount of adding aluminum nitride indicating that the incorporated aluminum substituted smaller silicon atoms. After post-HIP treatment, lattice parameter then decreased with nitrogen gas pressure. The piezoresistive coefficient increased with the addition of aluminum nitride, it further increased with the nitrogen doping pressure.     

Tensile behavior of polypropylene blended with bimodal distribution of styrene‐ethylene‐butadiene‐styrene particle size

The objective is to characterize the effects of the bimodal distribution of rubber particles and its blend ratio on the mechanical properties of the thermoplastic polypropylene blended with two different styrene‐ethylene‐butadiene‐styrene triblock copolymer at the intermediate and high strain rates. Tensile tests are conducted at the nominal strain rates from 3 × 10^?1 to 10² (1/s). Phase morphology is investigated to estimate the bimodal rubber particle size distribution. In addition, the in situ observation is conducted during uniaxially stretching within transmission electron microscopy step by step to investigate the deformation events depending on the elongation of samples. The elastic modulus increased gradually as the blend ratio of large rubber particle increased. An increase in the rupture strain and the strain energy up to failure was found for the bimodal rubber particle distributed blend system where the blend ratios of small rubber particle and large rubber particle were same. This is because the smaller particles dominant blend systems show the bandlike craze deformation while the localized plastic deformation is taken place in the larger particles dominated blend systems. The synergistic effect of these rubber particles gives rise to a strong increase in the ductility of these bimodal rubber particle distributed polypropylene systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008