Preparation and photoluminescence properties of γ-KCaPO4: Eu phosphors for near UV-based white LEDs

Novel whitish-blue phosphors based on a phosphate host matrix, γ-KCaPO₄: Eu²⁺, were prepared by a conventional solid-state reaction method using slightly phosphorus deficient conditions and their photoluminescence properties were investigated. The concentration quenching process, temperature dependence of the luminescence and decay curve were also investigated. The γ-KCaPO₄: Eu²⁺ phosphor was efficiently excited by UV-Visible light at wavelengths of 200-450 nm and exhibited a bright whitish-blue emission with a maximum peak wavelength of 473 nm. All of these characteristics suggest that the γ-KCaPO₄: Eu²⁺ phosphors combined with red phosphors could be applicable to near UV-based white LEDs, i.e., only two kinds of phosphor powders are needed for the formation of white light.     

Composite nanofiber of bioactive glass nanofiller incorporated poly(lactic acid) for bone regeneration

A novel composite nanofiber of poly(lactic acid) (PLA) incorporated with the nanocomponent of bioactive glass was exploited using an electrospinning method. Small concentrations of the bioactive glass phase added up to 10% facilitated the generation of a nanofibrous matrix with hundreds of nanometers in diameter without a formation of beads. The addition of the bioactive glass phase greatly enhanced the in vitro apatite formation on the nanofiber surface under a body simulating medium. Osteoblastic cells were demonstrated to adhere well on the composite nanofiber and grow actively with culturing time, suggesting its usefulness as a supporting matrix for the hard tissue regeneration.     

Photon statistics of single-mode zeros and ones from an erbium-doped fiber amplifier measured by means of homodyne tomography

We report measurement of the photon-number distributions of zeros and ones that emerge from an erbium-doped fiber amplifier (EDFA) in an on-off modulated communication system. Single-mode single-photon resolution was achieved by employing the method of optical homodyne tomography. The measured distributions agree with the quantum predictions of a Bose-Einstein distribution for the zeros and a Laguerre (noncentral negative binomial) distribution for the ones over a dynamic range up to 40 dB. The resulting noise figure of the amplifier compares well to that measured by an optical spectrum analyzer.     

Computer simulation of pitting potential measurements

A deterministic model for the growth of single pits in stainless steel has been combined with a purely stochastic model of pit nucleation. Monte-Carlo simulations have been used to compare the predictions of this model with potentiodynamic experimental measurements of the pitting potential. The quantitative agreement between model and experiment is reasonable for both 304 and 316 stainless steel, and the effects of varying surface roughness, solution chloride concentration and potential sweep rate have been considered.     

Removal of PM2.5 entering through the ventilation duct in an automobile using a carbon fiber ionizer-assisted cabin air filter

This study evaluated the charging characteristics of a carbon fiber ionizer for PM2.5 and carried out particle capture laboratory tests after an ionizer was installed upstream of the media of an electret cabin air filter. When the ion concentration per particle (N_i) of the carbon fiber charger was 10⁶ ions/cm³, the average charge numbers for each particle were 1.54, 0.88, and 0.49 at 0.6, 1.2, and 1.8 m/s of face velocity, respectively (the particle charging times, τ, were 167, 83, and 56 ms, respectively). For these face velocities, the PM2.5 removal efficiencies of the filter media were 69.3%, 65.2% and 62.2%, respectively, but increased to 80.4%, 71.2% and 65.5%, respectively, when the ionizer was turned on. The carbon fiber ionizer was then installed in front of an electret cabin filter in the air conditioning system of an automobile, after which field tests were performed at a roadside area. For the same N_iτ used in the lab-scale tests, the effects of the carbon fiber ionizer on increasing PM2.5 %Reduction were mild as 9.4%, 4.0%, and 2.8% when the flow rates were at the second, fourth, and sixth levels, respectively (the face velocities were 0.6, 1.2, and 1.8 m/s, respectively). The PM2.5 %Reduction can be substantially increased by 20–21%, for a higher value of N_iτ (=1.0×10⁸ ions s/cm³), which is realized by increasing the power consumption of the carbon fiber ionizer.     

Chromotropic ferrocenyl chalcone with two pyrenyl groups: Solvatochromism and molecular chemosensor for Fe(III)/Fe(II) ions

A chromotropic ferrocenyl chalcone with two pyrenyl groups (Fc-dPyr) is prepared and spectroscopically characterized. The X-ray structure analysis shows that the two pyrenyl groups are almost parallel to each other with a torsion angle of 5.57° and adopt a dimeric mode with a distance of 3.776 Å between them, ready to form an excimer. The solvatochromic fluorescence spectra indicate that the emission maxima observed in hydrogen-bonding donor (HBD) solvents (CHCl₃, EtOH and MeOH) exhibit a strictly linear relationship with the normalized E_T^N value, while those in a non-HBD solvent (CH₃CN) do not. The molecular chemosensor activity of Fc-dPyr is highly selective toward Fe(III) ions over Fe(II) ions. The fluorescence emission intensity of Fc-dPyr steeply decreases in the presence of Fe(III) ions as an oxidant, but not in the presence of Fe(II) ions.     

Failure mechanism for metal cylinder under explosive loading

This paper presents the numerical study of dynamic fracture for metal cylinder under internal explosive loading. Also, the effects of fracture models and groove designs on fracture behavior are investigated. For the dynamic hardening behavior, the Lim-Huh model including the thermal softening effect is adopted [1, 2]. Also, the Lou-Huh fracture model considering the strain rate dependency is used for fracture prediction [3]. The tensile fracture occurs first at the outer surface, and the shear fracture is observed near the inner surface. In addition, finite element analyses are performed to study the effect of various groove designs on dynamic fracture; single U-groove and V-groove at the outer surface. The tensile and shear fracture lines are predicted near the groove tip and inner surface, respectively. It is concluded that the stress triaxiality parameter is one of the critical factors in the dynamic fracture prediction of the metal cylinder.

     

Tunable 3D Nanoresonators for Gas‐Sensing Applications

The detection of gas species with high sensitivity is a significant task for fundamental sciences as well as for industrial applications. Similarly, the ongoing trend for device miniaturization brings new challenges for advanced fabrication including on‐demand functionality tuning. Following this motivation, here the additive, direct‐write fabrication of freestanding 3D nanoarchitectures is introduced, which can be brought into mechanical resonance via electric AC fields. Specifically, this study focuses on the 3D nanostructure synthesis, the subsequent determination of Young's modulus, and demonstrates a postgrowth procedure, which can precisely tune the material modulus. As‐fabricated resonators reveal a Young's modulus of 9–13 GPa, which can be increased by a factor greater than 5. Next, the electric readout of the resonance behavior is demonstrated via electric current measurement as an essential element for the resonance sensor applications. Finally, the implications of gas‐physisorption and gas‐chemisorption on the resonance frequencies are studied, representing a proof‐of‐principle for sensing applications by the here presented approach.     

Thermal kinetics of color degradation of mulberry fruit extract

The effects of temperature and pH on color degradation kinetics of the mulberry fruit extract were investigated. The absorbance at 510 nm was decreased with increase of heating time, but that at 420 nm was increased with the increase of heating time at 100 degrees C. The change of the browning index (A510/A420) was increased with increase of pH and was lower at pH 2.0 than that at pH 5.0. The browning index variation was adequately described by both the first-order and the zero-order kinetic. However, the zero-order kinetic model was proposed because of the better fit. According to the Arrhenius model, the activation energies for the browning index in the range of 80-100 degrees C for the four different pH values were 30.68 kJ/mol for pH 2.0, 35.87 kJ/mol for pH 3.0, 42.67 kJ/ mol for pH 4.0, and 43.49 kJ/mol for pH 5.0.     

Ionic liquid mediated synthesis of silica/polystyrene core–shell composite nanospheres by radical dispersion polymerization

This report describes the novel preparation of silica/polystyrene (SiO₂/PS) core–shell composite nanospheres by in situ radical dispersion polymerization in an ionic liquid (IL). Silica nanoparticles were first surface modified by the silane coupling agent methacryloxypropyltrimethoxysilane (MPTMS), which is capable of copolymerizing with styrene and provided a reactive CC bond. Transmission electron microscopy (TEM) revealed core–shell morphology with smooth surfaces. X-ray photoelectron spectroscopy (XPS) analysis demonstrated that almost all of the SiO₂ nanoparticles were encapsulated by the polymer. The composite particles were also analyzed by FT-IR spectroscopy and thermogravimetric analysis (TGA). In principle, this simple and environmentally-friendly synthetic procedure can be employed to prepare other inorganic oxide-containing polymer composites.