Electrical properties of silane crosslinked polyethylene incomparison with DCP crosslinked polyethylene

The electrical properties such as water tree length, electrical conduction, ac breakdown strength and space charge of silane crosslinked polyethylene (SXLPE) were investigated, with a purpose to compare this material with ordinary dicumyl peroxide (DCP) crosslinked polyethylene (XLPE). Experimental results show that SXLPE has a smaller water tree length, much lower conduction current density, a little bit higher ac breakdown strength than XLPE, and on SXLPE only a very small homocharge is seen. The better behaviour of SXLPE under electric stress is attributed to the absence of residual curing byproducts present in XLPE and the change of chemical structure by grafting and curing reactions     

A short-term,hydroponic-culture of ginseng results in a significant increase in the anti-oxidative activity and bioactive components

Food Science and Biotechnology - Panax ginseng CA Meyer has a variety of biological effects, including antioxidant and antidiabetic activities. Ginseng requires long-term cultivation, but this can...     

Anti-inflammatory and in vitro bone formation effects of Garcinia mangostana L. and propolis extracts

Food Science and Biotechnology - The purpose of this study was to determine the anti-inflammatory and in vitro bone formation effects of Garcinia mangostana L. (mangosteen) and propolis extracts....     

Rheological Characteristics of Fibrinogen-Thrombin Solution and Its Effects on Surimi Gels

Gel enhancing effects of fibrinogen-thrombin on surimi were investigated using failure stress and analyzed by mixture design. Gelation time of fibrinogen-thrombin mixture (20:1) gradually decreased as temperature increased from 5 to 40°C, whereas the G′ and G″ values continued to decrease up to 30°C and then increased at >30°C. Low quality surimi produced higher textural values (stress and strain) when fibrinogen and thrombin mixture (3–5%) had been added. Nonlinear stepwise regression model showed no significant interaction effects between surimi and fibrinogen-thrombin mixture. However, the response trace plot showed that failure stress value of surimi gel was increased by the concentration of fibrinogen-thrombin, but decreased by water content.     

A stabilized conforming nodal integration for Galerkin mesh‐free methods

Domain integration by Gauss quadrature in the Galerkin mesh‐free methods adds considerable complexity to solution procedures. Direct nodal integration, on the other hand, leads to a numerical instability due to under integration and vanishing derivatives of shape functions at the nodes. A strain smoothing stabilization for nodal integration is proposed to eliminate spatial instability in nodal integration. For convergence, an integration constraint (IC) is introduced as a necessary condition for a linear exactness in the mesh‐free Galerkin approximation. The gradient matrix of strain smoothing is shown to satisfy IC using a divergence theorem. No numerical control parameter is involved in the proposed strain smoothing stabilization. The numerical results show that the accuracy and convergent rates in the mesh‐free method with a direct nodal integration are improved considerably by the proposed stabilized conforming nodal integration method. It is also demonstrated that the Gauss integration method fails to meet IC in mesh‐free discretization. For this reason the proposed method provides even better accuracy than Gauss integration for Galerkin mesh‐free method as presented in several numerical examples. Copyright © 2001 John Wiley & Sons, Ltd.     

Physical and potentiometric properties of polyurethane‐based cation‐selective membranes

Lipophilic salts based on tetraphenylborate derivatives [e.g., potassium tetrakis(p‐chlorophenyl)borate (KTpClPB), sodium tetraphenylborate (NaTPB), and cesium tetrakis(3‐methylphenyl)borate are essential ingredients used in the preparation of solvent polymeric cation‐selective membranes. The effects of such lipophilic salts on the physical properties of a polyurethane (PU) matrix comprising 4,4′‐diphenylmethane diisocyanate, 1,4‐butanediol, and poly(tetramethylene ether glycol) were examined. Differential scanning calorimetry measurements revealed that the sodium and potassium salts doped in PU increased the glass‐transition temperatures (T_g) of the matrix, while the film containing cesium salt exhibited slightly decreased T_g. The temperature dependence of the ionic conductivity for PU60 films doped with KTpClPB is well described by the Arrhenius‐type equation, and that doped with NaTPB is described by the Vogel–Tammann–Fulcher (VTF)‐type equation. The temperature dependence of the ionic conductivity on the VTF‐type equation suggests that the transport of sodium ions in the PU60 matrix is more strongly coupled to the soft segmental motion, and potassium ions are decoupled from the polymer host and transported by activated hopping. The effect of added salt on the internal structure of PU membranes was investigated by measuring the ratio between the free and hydrogen‐bonded CO bands at 1703 and 1730 cm⁻¹, respectively. The results showed that the ether oxygens in the soft segment chains are strongly coupled to the potassium or sodium, but much less to cesium. The potentiometric properties of these lipophilic additive doped PU membranes were characterized by incorporating valinomycin and 4‐tert‐butylcalix[4]arene‐tetraacetic acid tetraethylester as potassium‐ and sodium‐selective ionophores, respectively. Their response behavior could be explained by the observed physical characteristics. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 618–625, 2001     

Pure‐Red Dye for Organic Electroluminescent Devices: Bis‐Condensed DCM Derivatives

In this paper, the bis‐condensed 4‐(dicyanomethylene)‐2‐methyl‐6‐[p‐(dimethylamino)styryl]‐4H‐pyran ( DCM) derivatives are introduced as a new class of red dye for organic light‐emitting devices (OLEDs). They showed more red‐shifted emission than the mono‐substituted DCM derivatives and the emission maxima increased as the electron‐donating ability of the aromatic donor group increased. On the basis of these results, red light‐emitting devices were fabricated with bis‐condensed DCM derivatives as red dopants. For a device of configuration ITO/TPD/Alq₃ + DADB (5.2 wt.‐%)/Alq₃/Al (where ITO is indium tin oxide, TPD is N,N′‐diphenyl‐N,N′‐bis(3‐methylphenyl)‐1,1′‐biphenyl‐4,4′‐diamine, Alq₃ is tris(8‐hydroxyquinoline) aluminum, and DADB is [2,6‐bis[2‐[5‐(dibutylamino)phenyl]vinyl]‐4H‐pyran‐4‐ylidene]propanedinitrile), pure red emission was observed with Commission Internationale de l’Eclairage (CIE 1931) coordinates of (0.658, 0.337) at 25 mA/cm².     

Specific approaches to dramatic reduction in stack activation time and perfect long-term storage for high-performance air-breathing polymer electrolyte membrane fuel cell

Air-breathing polymer electrolyte membrane fuel cell (PEMFC) systems without the humidifier and air blower have been developed to overcome the cost and complexity of balance of plants (BOPs). Until now, there has been no specific way to improve the stack's initial performance through the specific activation protocol and maintain the initial performance for a very long time. Herein, we studied a technique for finishing the total activation within 1 h by using a pre-activation process (i.e., soaking the stack in a DI-water reservoir) and applying current at 0.65 V. The pre-activation procedure significantly increased the swelling of the polymer membrane and the Nafion binder in the catalyst layer, reducing the total activation time. Also, we showed that long-term storage using humidified N₂ gas in a closed box did not hinder the electrocatalytic activity of the Pt and the drying of the polymer membrane for 60 days.     

Improved performance of molten carbonate fuel cells with (Li/Na)2CO3 electrolytes by using BYS coated cathode at low operating temperatures

In order to improve the stack life time of MCFCs, it is necessary to reduce the operating temperature of MCFCs below 600 °C, because reduced operating temperature minimizes electrolyte loss due to evaporation and corrosion. However, at the low operating temperature below 600 °C, the cell performance of MCFCs with (Li/Na)₂CO₃ electrolyte is too low to operate the fuel cell stack and system. In this study, we have performed wettability control of the liquid molten carbonate electrolyte by coating NiO cathodes with poor wetting property of the mixed ionic and electronic conductor (MIEC) such as BYS (Bi_1.5Y_0.3Sm_0.3O_3-δ). From experiments with symmetrical cells, each polarization component with various temperatures and gas conditions were studied. To investigate effects of the BYS coated cathode on the performance of MCFCs, a 100 cm² single cell of MCFCs was employed. The performance of a 100 cm² single cell with BYS coated cathode was better than that with conventional cathode by a factor of 1.84, because BYS coated cathode reduces activation polarization and mass transfer resistance greatly.     

One‐dimensional analysis of thin‐walled closed beams having general cross‐sections

This paper presents a new one‐dimensional theory for static and dynamic analysis of thin‐walled closed beams with general cross‐sections. Existing one‐dimensional approaches are useful only for beams with special cross‐sections. Coupled deformations of torsion, warping and distortion are considered in the present work and a new approach to determine sectional warping and distortion shapes is proposed. One‐dimensional C⁰ beam elements based on the present theory are employed for numerical analysis. The effectiveness of the present theory is demonstrated in the analysis of thin‐walled beams having pillar sections of automobiles and excavators. Copyright © 2000 John Wiley & Sons, Ltd.