Synthesis and Fluorescence Properties of Eu2+-Complex-Doped SiO2 Gels

Eu²⁺-complex-doped SiO₂ gels were prepared and their fluorescence properties were studied. SiO₂ gels were obtained by the reactions of silicon tetrachloride, tert -butyl alcohol, and methyl alcohol under nitrogen. Both to protect Eu²⁺ against oxidation and to enhance the emission intensity of Eu²⁺, Eu²⁺ was complexed with 15-crown-5 or its derivative. Samples showed blue emission. Fluorescence lifetimes of samples varied from 690 to 955 ns depending on the Eu²⁺ concentration at 290 K. After drying of samples, 50-70% of Eu²⁺ remained in the divalent state without oxidation in the samples. It was found that Eu²⁺ complexes inside gels were stable against oxidation in air.     

Direct contact melting with asymmetric load

In this study, direct contact melting with an asymmetric load was investigated both experimentally and by numerical analysis. A rectangular parallelepiped solid on a heating surface was melted under various asymmetric loads, while total load acting on the solid and brine temperature were kept constant. In the numerical analysis, the melting process keeping the force balance between the pressure in the liquid film and the loads at all times was calculated. It was found that the average heat flux into the solid was independent of the moment acting on the solid. Analytical results of the time dependencies of the amount of melting and the inclination of the solid agreed with experimental ones for each condition.     

A Single-Chip Ultra-Wideband Receiver With Silicon Integrated Antennas for Inter-Chip Wireless Interconnection

A single-chip ultra-wideband (UWB) receiver was developed using 0.18 mum CMOS technology, and inter-chip wireless data communication by integrated antennas was confirmed. Timing pulse and data pulse with on-off keying were alternately sent from a transmitting antenna. Double Gaussian monocycle pulse (GMP) template generators performed detections of timing and data pulses. A single GMP template, whose probability distribution of the pulse repetition cycle is given by Gaussian, showed a random jitter of 4.87 ps. Dual-Dirac model could explain the probability distribution of the cycle of double GMP template. Obtained random jitter and deterministic jitter were 4.6 ps and 14.4 ps, respectively. The receiver successfully recovered 200 Mbps data at the distance of 0.5 mm.     

Influences of the alkoxy group number and treatment condition on the structure of glycidoxy functional silane-treated layer on silica particles analyzed by 1H pulse NMR

The surface treatment of spherical silica particles using a silane coupling agent with a glycidoxy group was conducted and the effect of the alkoxy group number on the molecular mobility of the silane chain was investigated by ¹H pulse nuclear magnetic resonance (NMR). Silanes with di-alkoxy and tri-alkoxy structures were used, and the silica particles were treated with 2-propanol solution and heated at 120?°C for 24?h after solvent evaporation. The surface coverage of the silica surface was in the range from two to three layers. For multilayer coverage, linear chain and network structures were expected to form on the surface by polycondensation reaction using the di- and tri-alkoxy structures, respectively. However, the relaxation times for silane chains with both di- and tri-alkoxy structures measured by pulse NMR were short, which indicates that both silane chains formed rigid network structures. Fourier transform infrared spectroscopic analysis revealed that ring opening of the epoxy group occurred, followed by reaction to form the network structure, even with the di-alkoxy structure. Ring opening of the epoxy group could be reduced by setting the heating temperature at 80?°C. There was a significant difference in flexibility between the silane-layers with di- and tri-alkoxy structures after heating at 80?°C, as reflected by the relaxation time.     

芝加哥滨河步道扩建

<正>芝加哥河主干河道有着悠久且丰富的历史,它在很多方面映射了芝加哥城市的发展。芝加哥河以前是一条蜿蜒的沼泽溪流,后来被硬化改造为工程河道以支持城市向工业型的转换。1900年,为了改善公共卫生状况,城市将河流主干与南侧分支水流方向倒转。在此之后,此条河道声名鹊起。建筑师、城市设计师丹尼尔·伯纳姆提出了滨河散步道     

Ultra-thin film photodiodes for use in position sensors

Abstract

A novel optical interferometer based on detecting the standing wave is realized by the newly developed ultra-thin film photodiode. The active layer of the ultra-thin film photodiode is thinner than half the wavelength of the incident light. Only a small part of the incident light is absorbed and the rest passes through the photodiode. This ultra-thin film photodiode can detect the intensity profile of the interference fringe of the standing wave, being inserted in the optical field. Taking advantage of this function, a compact interferometer having no reference arm is realized. The principle, design, fabrication, and performance as the displacement sensor are described. The signal obtained confirms the feasibility of this new interferometer. The displacement direction is also detected by a dual ultra-thin film photodiode with a phase shifter comparing the phases of the two signals.     

Entropic effect on creep in nanocrystalline metals

We report a significant entropic effect on creep of nanocrystalline metal using molecular dynamics. Our simulations reveal that the activation entropy may contribute a multiplicative factor of many orders of magnitude to the steady-state creep rate. The relationship between activation entropy and enthalpy obeys an empirical Meyer–Neldel compensation rule. The activation volume is found to decrease with increasing temperature for dislocation nucleation creep, which agrees well with experimental results. The study opens up an avenue for quantitatively discussing the entropic effects on various thermally activated deformations in nanocrystals.     

Dewatering of high-moisture wood chips by roller compression method

In seeking an efficient method for drying very wet chips, we developed and tested an original continuous dewatering system using mechanical compression (10–30 MPa). The moisture content of cedar chips decreased from 100–270% to 85–130% (dry basis), and the energy required to remove the water was 9% (power consumption basis) and 25% (primary energy basis) for heat energy to evaporate the water. In the case of combined drying, in which roller compression was applied first, followed by thermal drying, the energy required to dry wet cedar chips to a moisture content as low as 20% was 49% (power consumption basis) and 58% (primary energy basis) of that required for thermal heating alone. These results indicate that the combined method uses less energy to dry very wet wood chips.