Transient characteristics of organic light-emitting diodes with efficient energy transfer in emitting material

We have investigated the combination effect of host–guest materials in an emitting layer on the transient property of an organic light-emitting diode (OLED). We found that an efficient energy transfer owing to the large overlap between the photoluminescence spectrum of host material and the absorption spectrum of guest material was an important factor to improve the response speed of the OLED. As a result, the rise time of optical response was mainly affected by the combination of host–guest materials, and it increased using the optimal guest material, 1,4-bis[2-[4-N,N-di(p-tolyl)amino]phenyl]vinyl]benzene (DSB). A maximum −3 dB cutoff frequency of 15.8 MHz was achieved for an OLED with DSB as a guest material.     

Influence of Particle Velocity on Adhesion of Cold-Sprayed Splats

In cold spray, innovative coating process, powder particles are accelerated by a supersonic gas flow above a certain critical velocity. Particles adhesion onto the substrate is influenced by particle impact velocity, which can change dramatically depending on particle position from the core of the jet. In the present work, an original experimental set-up was designed to discriminate the particles as a function of the levels of velocity to investigate the influence of this parameter on adhesion. Particles at given positions could therefore be observed using scanning electron microscope, which showed different morphologies as a function of impact velocity. High pressure and temperature at the interface during impact were calculated from numerical simulations using ABAQUS^®. Transmission electron microscope analyses of thin foils were carried out to investigate into resulting local interface phenomena. These were correlated to particle impact velocity and corresponding adhesion strength which was obtained from LAser Shock Adhesion Test.     

Structures of liquid crystalline wholly aromatic copolyester films with different copolymer compositions

Films of wholly aromatic copolyester composed of 4-hydroxybenzoic acid (HBA) and 2-hydroxy-6-naphthoic acid (HNA) were prepared by a solution-casting method using a mixed solution of pentafluorophenol (PFP) and chloroform (weight ratio: PFP/chloroform = 3/7). Using five samples with different copolymer compositions (HBA/HNA [mol%] = 25/75, 40/60, 55/45, 62/38, 73/27), the effects of the copolymer composition on the fine structures of the films were investigated using thermal analyses, density measurements, X-ray diffraction methods, and tensile tests. The as-cast films obtained were shown to be trans-parent and highly amorphous in spite of changing the copolymer composition. When the films were heated above the T_g (100°C), cold crystallization first occurred during the heating process and they had melting points. The densities of the films increased with increasing annealing temperature throughout the cold crystallization. The elongation percentages of the as-cast films reached high values of 30–74% at room temperature, indicating their maximum of elongation at 55 mol% of HBA. © 1996 John Wiley & Sons, Inc.     

High-Temperature Properties of Unburned MgO-C Bricks Containing Al and Si Powders

Changes in the mechanical and thermal properties, as well as in the microstructure, of unburned MgO-C bricks containing Al and Si powders were investigated at selected temperatures. Specimens with heat treatments at 500°C shrank and exhibited higher apparent porosity than untreated specimens. The bending strength and elastic modulus at 500°C were much lower than those of untreated specimens, and the apparent porosity increased and the mechanical properties at 500°C decreased with each repeating heat treatment. It was predicted that when the volatile matter was no longer generated, microstructure shrinkage would stop and the mechanical properties become constant. The bending strength and static elastic modulus at 800°, 1000°, and 1300°C were higher than those at 500°C because of the binding effect of the reaction products (i.e., Al₄C₃, SiC, and MgAl₂O₄), although the apparent porosity was higher than at 500°C. Repeated heat treatment from room temperature (RT) to the respective temperature, however, degraded the properties to nearly the same level as at 500°C because of the increased apparent porosity and the cracks generated in magnesia particles by the reaction products. Plastic deformation appeared to occur at 1300°C just before bricks were fractured. In addition, the thermal expansion ratio decreased through repeated heating and cooling from RT to 500°, 1000°, or 1300°C, and finally decreased to a constant value, as predicted.     

Densification of Sol-Gel-Derived Mullite Ceramics after Cold Isostatic Pressing up to 1 GPa

Molecular-designed ultrafine mullite precursor powders with a stoichiometric composition were prepared by copolymerization of alkoxides. The precursor powders were calcined in the range from 800° to 1200°C and consolidated by ultra-high-pressure cold isostatic pressing up to 1 GPa. Ultrahigh isostatic pressure of 1 GPa led to a closed packing structure in the green compacts. Interaggregate pores in the green compacts were collapsed by the ultrahigh cold isostatic pressure to reduce the pore size below 6 nm. As a result, the maximum density of the green compacts reached 70% of theoretical. These closely packed green compacts of precursor powders with a stoichiometric composition and calcined at relatively low temperatures could be sintered to >95% of theoretical at 1500°C. Relatively low-temperature sintering below the liquid formation temperature resulted in fine microstructure of the resultant mullite ceramic with a grain size below 300 nm.     

Detection of patulin in apple juices marketed in the Tohoku district, Japan

Patulin is a mycotoxin mainly produced by Penicillium and Aspergillus. We investigated the incidence of patulin contamination in 179 samples of apple juice and 9 samples of mixed juice (containing apple juice concentrate as an ingredient) commercially available in the Tohoku district of Japan. Patulin was detected in 3 of 143 samples containing domestic fruits and in 6 of 45 samples containing imported products and products produced in Japan using imported apple juice concentrate. Patulin analyses were carried out using high-pressure liquid chromatography with a detection limit of 4 microg/liter. The patulin content of contaminated domestic samples (three samples with concentrations ranging from 6 to 10 microg/liter), imported samples (one sample with a concentration of 15 microg/liter), and domestic samples produced containing imported concentrate (five samples with concentrations ranging from 6 to 9 microg/liter) was lower than the maximum limit of 50 microg/liter currently adopted by many countries, including Japan.     

体育环境论 ——“可以看得到的”体育设施使城市更加富有活力

仙田满通过近年来的系统性研究 和针对体育建筑扎实的观察和实践,将环 境、人、活动、空间这几者相互关系进行精 细化设计,提供给体育设施的使用者、管理者 充分满足功能要求且独具特色的体验。本文 针对与运动相关联的环境中不同的人群在不 同空间的使用场景进行分类,通过“可以看 得到的”的可视化设计手法、结合游戏环境 的设计七要素,着重强调设计中“空间趣味 性”的“循环连续性”所创生的多样性;通过 “使用者角度”的关系场景拓扑,设计出“运 动员最优先”的参赛体验,同时为观众创造出 多样的观赛场景;通过“开放式场馆”可开 闭设计手法、创造出内外积极融合的空间变 化契机,带给设施使用者惊喜。体育设施的 设计匠心,在构思细部中得以体现,演变出无 数令人流连忘返的精彩时空瞬间。     

Stable and Selective Dehydrocondensation of Methane Towards Benzene on Modified Mo/HMCM-22 Catalyst by the Dealumination Treatment

A modified Mo/HMCM-22 catalyst by the dealumination treatment (Mo/HMCM-22-D) exhibited remarkable performance for the catalytic dehydrocondensation of methane with a higher selectivity of benzene and a lower selectivity of coke, in comparison with the same Mo catalyst supported on parent HMCM-22 (Mo/HMCM-22). Excellent catalytic stability as well as a high benzene formation rate of 1500 nmol/(g-cat·s) was obtained on a 6%Mo/HMCM-22-D catalyst at 1023 K, 3 atm and 2700 ml/(g·h) owing to the efficient suppression of coke formation. Dealumination of the HMCM-22 zeolite was characterized by XRD, ²⁷Al and ¹H MAS NMR and NH₃-TPD techniques. It was found that the dealumination treatment of HMCM-22 zeolite resulted in an effective suppression of acid sites, particularly the Brønsted acid sites (proton form in Al--O--Si) owing to the removal of tetrahedral framework aluminum, while the microporous structure and the zeolite framework remained unchanged. It was suggested that the stable and selective dehydrocondensation of methane towards benzene is based on the suppression of coke formation owing to the effective decrease of strong Brønsted acid sites by the dealumination treatment of the HMCM-22 zeolite.     

Synthesis of electrochemically and thermally stable amorphous hole-transporting carbazole dendronized fluorene

A novel amorphous hole-transporting carbazole dendrimer, 2,7-bis[3,6-di(carbazol-9-yl)carbazol-9-yl]-9,9-bis-n-hexylfluorene (G2CF), was synthesized by a divergent approach involving bromination and Ullmann coupling reactions. G2CF showed UV–vis absorption bands at 304 and 332 nm in chloroform solution and the photoluminescence spectra showed a maximum peak at 373 nm in a bluish-purple region. Differential scanning calorimetry (DSC) and cyclic voltammetry (CV) analysis revealed G2CF was an electrochemically and thermally stable amorphous material with a high glass transition temperature (T_g) of 237 °C. The organic light-emitting device having the structure of ITO/G2CF/Alq₃/LiF:Al exhibited a bright green emission with a maximum luminescence of 11,000 cd/m² at 16 V and a turn-on voltage of 5.4 V.     

Raw-starch Digestion by Chalara paradoxa Immobilized in Calcium Alginate Gels

The spores of raw starch digesting fungus Chalara paradoxa were entrapped in calcium-alginate beads and preincubated in growth medium. The fungus devoloped a mycelium layer below and on the gel bead surface so that nutrition and oxygen in this area had direct contact with mycelia. The fungus on the bead could produce amylase and could digest raw corn starch continuously for 40 d with corn steep liquor as a nitrogen source.