One-electron redox reaction of di-tert-butyl nitroxide at platinum electrode in acetonitrile

The electrochemical oxidation of di-tert-butyl nitroxide (DTBN) at a platinum electrode in acetonitrile was examined. The cyclic voltammogram indicated an irreversible response during a normal time scale measurement, whereas chemically reversible voltammograms were obtained during a shorter time using a micro disk electrode with relatively fast sweep rates. The apparent formal redox potential and heterogeneous electron transfer rate constant were estimated to be 0.218 V (versus Fc⁺|Fc) and 0.035 ± 0.015 cm s⁻¹ from the digital simulation analysis.     

Direct determination of the experimentally observed penetration depth of the evanescent field via near-infrared absorptions enhanced by the off-resonance of surface plasmons

Recently, absorption-sensitive surface plasmon resonance (SPR) techniques have attracted much attention. SPR near-infrared spectroscopy (SPR-NIRS) based on the Kretschmann configuration is one of the techniques for absorption enhancement. The enhanced spectrum obtained by SPR-NIRS basically corresponds to the measurement of an NIR absorption spectrum with a very short path length. However, the path length cannot be applied for Lambert's law due to the enhanced evanescent field. A direct determination of the penetration depth of the evanescent field is carried out via NIR absorptions enhanced by the off-resonance of surface plasmons, which is a principle of SPR-NIRS. The signal intensities of the enhanced NIR spectra of micrometer-thick polymer films having various thicknesses are compared with the classic theory of penetration depth. It is confirmed that the effective depth of the SPR-NIRS measurement can be expressed by the classic theory of penetration depth of the evanescent field proposed by Harrick.     

Fabrication of ferromagnetic Ni epitaxial thin film by way of hydrogen reduction of NiO

The ferromagnetic epitaxial Ni (111) thin film on the oxide substrate could be obtained by an epitaxy method, employing pulsed laser deposition (PLD) of epitaxial NiO (111) film on the sapphire (α-Al₂O₃) substrate and successive hydrogen reduction. The epitaxial NiO (111) film was deposited on the sapphire (0001) substrate at room temperature by PLD, and was reduced into the Ni epitaxial film by annealing (300 °C to 700 °C) in the hydrogen atmosphere, suggesting the possible formation of epitaxial [Ni metal/α-Al₂O₃] multilayer. The epitaxy of Ni film was proved by ex situ X-ray diffraction. The ferromagnetic anisotropy of the epitaxial Ni film was examined by superconducting quantum interference magnetometry.     

Burning velocity measurements of nitrogen-containing compounds

Burning velocity measurements of nitrogen-containing compounds, i.e., ammonia (NH₃), methylamine (CH₃NH₂), ethylamine (C₂H₅NH₂), and propylamine (C₃H₇NH₂), were carried out to assess the flammability of potential natural refrigerants. The spherical-vessel (SV) method was used to measure the burning velocity over a wide range of sample and air concentrations. In addition, flame propagation was directly observed by the schlieren photography method, which showed that the spherical flame model was applicable to flames with a burning velocity higher than approximately 5 cm s⁻¹. For CH₃NH₂, the nozzle burner method was also used to confirm the validity of the results obtained by closed vessel methods. We obtained maximum burning velocities (S_u0,max) of 7.2, 24.7, 26.9, and 28.3 cm s⁻¹ for NH₃, CH₃NH₂, C₂H₅NH₂, and C₃H₇NH₂, respectively. It was noted that the burning velocities of NH₃ and CH₃NH₂ were as high as those of the typical hydrofluorocarbon refrigerants difluoromethane (HFC-32, S_u0,max = 6.7 cm s⁻¹) and 1,1-difluoroethane (HFC-152a, S_u0,max = 23.6 cm s⁻¹), respectively. The burning velocities were compared with those of the parent alkanes, and it was found that introducing an NH₂ group into hydrocarbon molecules decreases their burning velocity.     

用于空气中水蒸气吸-脱附的微孔泡沫炭制备研究

以蜜胺泡沫体为模板,采用氟化聚酰业胺制备了微孔泡沫炭.测定了其对环境中水气的吸附/脱附行为,发现:泡沫炭在空气中400℃活化1 h,可以提高其对水气的吸附能力.与活化前相比,对水气的吸附量几乎高达3倍,尽管其微孔容积仅增大了1.5倍.对环境水气中的可逆吸附率与微孔容积成线性关系,微孔容积为0.75mL/g的泡沫炭,其水气吸附率约为质最分数40%.     

An accurate and stable multiphase moving particle semi‐implicit method based on a corrective matrix for all particle interaction models

The Lagrangian moving particle semi‐implicit (MPS) method has potential to simulate free‐surface and multiphase flows. However, the chaotic distribution of particles can decrease accuracy and reliability in the conventional MPS method. In this study, a new Laplacian model is proposed by removing the errors associated with first‐order partial derivatives based on a corrected matrix. Therefore, a corrective matrix is applied to all the MPS discretization models to enhance computational accuracy. Then, the developed corrected models are coupled into our previous multiphase MPS methods. Separate stabilizing strategies are developed for internal and free‐surface particles. Specifically, particle shifting is applied to internal particles. Meanwhile, a conservative pressure gradient model and a modified optimized particle shifting scheme are applied to free‐surface particles to produce the required adjustments in surface normal and tangent directions, respectively. The simulations of a multifluid pressure oscillation flow and a bubble rising flow demonstrate the accuracy improvements of the corrective matrix. The elliptical drop deformation demonstrates the stability/accuracy improvement of the present stabilizing strategies at free surface. Finally, a turbulent multiphase flow with complicated interface fragmentation and coalescence is simulated to demonstrate the capability of the developed method.     

Development of a time-resolved attenuated total reflectance spectrometer in far-ultraviolet region

A far-ultraviolet transient absorption spectrometer based on time-resolved attenuated total reflectance (ATR) has been developed and tested for aqueous solutions of phenol and tryptophan in the region 170-185 nm. In this region, a stable tunable laser was not available, and therefore, white light from a laser-driven Xe lamp source was used. The time resolution, which was determined by the time response of a continuous light detector, was 40 ns. A new ATR cell where a sample liquid is exchanged continuously by a flow system was designed to reduce efficiently the stray light from the excitation light. We have tested the performance of the instrument by using aqueous solutions of phenol and tryptophan, whose photochemistry is already well known. Phenol and tryptophan have very strong absorptions due to a π-π? transition near 180 nm. Even for dilute solutions (10(-3) mol dm(-3)), we could observe decreases in their concentrations due to photochemistry that occurred upon their irradiation with a fourth harmonic generation laser pulse produced by an Nd:YAG laser. The sensitivity of the spectrometer was about 10(-4) abs, which corresponded to a concentration variation of 10(-3) mol dm(-3) for phenol and tryptophan.     

See-through Detection and 3D Reconstruction Using Terahertz Leaky-Wave Radar Based on Sparse Signal Processing

We experimentally demonstrate see-through detection and 3D reconstruction using terahertz leaky-wave radar based on sparse signal processing. The application of terahertz waves to radar has received increasing attention in recent years for its potential to high-resolution and see-through detection. Among others, the implementation using a leaky-wave antenna is promising for compact system integration with beam steering capability based on frequency sweep. However, the use of a leaky-wave antenna poses a challenge on signal processing. Since a leaky-wave antenna combines the entire signal captured by each part of the aperture into a single output, the conventional array signal processing assuming access to a respective antenna element is not applicable. In this paper, we apply an iterative recovery algorithm “CoSaMP” to signals acquired with terahertz leaky-wave radar for clutter mitigation and aperture synthesis. We firstly demonstrate see-through detection of target location even when the radar is covered with an opaque screen, and therefore, the radar signal is disturbed by clutter. Furthermore, leveraging the robustness of the algorithm against noise, we also demonstrate 3D reconstruction of distributed targets by synthesizing signals collected from different orientations. The proposed approach will contribute to the smart implementation of terahertz leaky-wave radar.     

Electrochemical behavior and electrodeposition of dysprosium in ionic liquids based on phosphonium cations

The electrochemical behavior and the electrodeposition of dysprosium (Dy) in phosphonium-cation-based ionic liquid were investigated in this study. A new group of the room-temperature ionic liquids (RTILs) based on phosphonium cations with bis(trifluoromethylsulfonyl)amide anions was applied as novel electrolytic solutions. The cyclic voltammetric measurements resulted in one step reduction of the trivalent dysprosium ion in phosphonium-cation-based ionic liquid. On the other hand, no anodic peak ascribed to the oxidation of dysprosium metal was observed in this electroanalytical study. The diffusion coefficient and the activation energy for diffusion of the trivalent Dy complex in IL were estimated using semi-integral analysis, because it is important to analyze the diffusion properties to recover Dy through electrowinning methods. The diffusion coefficient of Dy(III) which was calculated to be 2.0 × 10⁻¹² m² s⁻¹ at 25 °C, closed to that of the trivalent lanthanoid ion such as Eu(III) and Sm(III) in phosphonium-cation-based ionic liquid. In addition, the activation energy for diffusion was estimated to be 65 kJ mol⁻¹ (0.5 M) and 49 kJ mol⁻¹ (0.075 M). The estimated activation energy for diffusion was affected by the concentration of the electrolytic solution, since the RTILs had relatively strong electrostatic interactions between the metal cations and the solvent anions. Furthermore, the electrodeposition of Dy in phosphonium-cation-based IL was carried out using a two-electrode system constructed with a copper plate cathode and dysprosium metal anode. Energy dispersive X-ray analysis of electrodeposits showed a sharply peaked spectrum corresponding to the characteristic X-ray lines of Dy. In addition, the obtained Dy, with the exception of the surface layer, was confirmed to be in the metallic electronic state by X-ray photoelectron spectroscopy.     

Use of compact shield tunneling method in urban underground construction

In Tokyo Metropolis, the rehabilitation and renewal of sewer systems is an urgent issue due to the aged sewers and increases in wastewater and stormwater runoff. In such urban area, shield tunneling confronts various problems, such as high construction costs, adverse effects on living environments, and densely used surface and underground spaces. To solve these problems, the authors developed a new shield tunneling method, which is called the “compact shield” method. This paper describes the concepts used for the construction of shield sewer tunnels without inner linings and an overview of the segments and a shield machine that were newly developed.