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This study aims to identify the key factors governing the thermal quenching of Mn4+ion luminescence in fluoride-based phosphor materials used as red emitters in modern-day phosphor-converted LED devices. Here, we employ first-principles calculations for Mn4+-doped Na2SiF6, NaKSiF6, and K2SiF6hosts to explore how host properties and local coordination environments influence thermal quenching behavior. The ΔSCF method was used to model the geometric structures of the Mn4+4A2(ground) and 2E, 4T2(excited) states and the energies of the optical transitions between these states. Our results reveal that thermal quenching in Na2SiF6and K2SiF6phosphors occurs through thermally activated 2E → 4T2→ 4A2crossover. In contrast, thermal quenching in NaKSiF6is due to other nonradiative decay pathways. Investigations of the mechanical stability of these fluorides show that NaKSiF6is mechanically unstable. We suggest that this property of the host limits the luminescence efficiency of the embedded Mn4+ions. We also determined the reason for the difference in the intensity of the 2E → 4A2emission transition (ZPL) in the systems. These findings advance our fundamental understanding of the thermal quenching mechanism of Mn4+ion luminescence in fluorides, and the results can aid future discoveries of technologically useful phosphors through high-throughput design methodologies.

Designing new materials with desired properties is a complex and time-consuming process. One of the most challenging factors of the design process is the huge search space of possible materials. Machine learning methods such as k-nearest neighbors, support vector machine (SVM) and artificial neural network (ANN) can contribute to this process by predicting materials properties accurately. Properties of multi-principal element alloys (MPEAs) highly depend on alloys’ phase. Thus, accurate prediction of the alloy’s phase is important to narrow down the search space. In this paper, we propose a solution of employing SVM method with hyperparameters tuning and the use of weighted values for prediction of the alloy’s phase. Using the dataset consisting of the experimental results of 118 MPEAs, our solution achieves a cross-validation accuracy of 90.2%. We confirm the superiority of this score over the performance of ANN statistically. On the other dataset containing 401 MPEAs, our SVM model is comparable to ANN and exhibits 70.6% cross-validation accuracy. We also found that additional variables, including average melting temperature and standard deviation of melting temperature, increase prediction accuracy by 3.34% in the best case.

Organo-halide perovskite solar cells (PSCs) are lightweight and low cost, and they offer high power conversion efficiencies. PSCs have proven to be useful in terrestrial applications. In addition, they are particularly attractive for space applications because they can offer a higher radiation tolerance than GaAs and Si solar cells. This paper evaluates the damage coefficient for minority-carrier diffusion length KLof perovskite crystals after 1 MeV electron irradiation by time-resolved photoluminescence measurements to investigate the reason for their high radiation tolerance. Results show that perovskite crystals have a lower damage coefficient KLthan that of InP crystals with a high radiation tolerance. On the other hand, first-principles calculations indicate that the displacement energy of perovskite crystals is as low as that of Si, which does not have a high radiation tolerance. The present results suggest that the annealing effect occurs for PSCs at room temperature.

A rapid and sensitive flow method, based on the combination of on-line solvent extraction with reversed micellar mediated chemiluminescence (CL) detection using rhodamine B (RB), was developed for the determination of antimony(III) and antimony(V) in aqueous samples. The on-line extraction procedure involved ion-pair formation of the antimony(V) chloro-complex anion with the protonated RBH+ion and its extraction from an aqueous hydrochloric acid solution into toluene, followed by phase separation using a microporous membrane. When in a flow cell of a detector, the ion-pair in the extract driven was mixed with the reversed micellar solution of cetyltrimethylammonium chloride in 1-hexanol-cyclohexane/water (0.60 mol dm−3H2SO4) containing cerium(IV), its uptake by the reversed micelles and the subsequent CL oxidation of RB with Ce(IV) occurred easily, then the produced CL signal was measured. Using the proposed flow method under the optimized experimental conditions, a detection limit (DL) of 0.35 μmol dm−3and a linear calibration graph with a dynamic range from DL to 16 μmol dm−3were obtained for Sb(V) with a precision of 1.4% relative standard deviation (n= 5) at the Sb(V) concentration of 8.2 μmol dm−3. The present method was successfully applied to the determination of Sb(V) in water samples and to the differential determination of Sb(III) and Sb(V) in copper electrolyte industrial samples, where total antimony Sb(III) + Sb(V) was determined after oxidation of Sb(III) to Sb(V) with Ce(IV) and Sb(III) was calculated by difference, for which the DL was almost the same as that for Sb(V).

Many human augmentation devices have been developed in the past few decades, but lots of them neglected the importance of well-timed assistance, which commonly leads to problems like lowered performance or interference with user's movement. In this research the authors focused in depth on the timing issue of powered assistance. As a pilot study for the proof of concept, the authors hypothesized that different timing of assistance may greatly affect the efficiency of movement for power-assisting devices, and verified the hypothesis through human experiment on sit-to-stand (STS) movement. By measuring the electromyogram (EMG) of lower limb muscles, the authors firstly confirmed the effectiveness of assistance, then compared the effect of assistance timing with other frequently investigated determinants of STS movement, and evaluated the efficiency of movement under different timing conditions. The results demonstrated the importance of timing in powered assistance, and showed that, rather than the common practice of providing assistance after the onset of movement, which is adopted by most traditional proportional-EMG-controlled human augmentation devices, it may improve the efficiency of movement for at least half of the subjects simply by adopting an earlier (before or at the same time of movement onset) but optimal timing for assistance. As a preparation for future works, the authors also quantitatively analyzed various early timing conditions, and the result indicated that if the authors could realize appropriate movement prediction mechanism, the performance of assistance may be improved further. Considering the generality of timing issue in many related works, these results could lead to a new direction of research on performance improvement of human augmentation devices.

We investigated the desorption of water from a TiO2 surface under a dry atmosphere by collecting the photoemission yield spectra with an open counter. For this purpose, a new attachment for the photoemission yield measurement was prepared. This apparatus is capable of detecting, in the open air, low-energy electrons excited by photons under dried atmospheres; the dew point is below -35°C. A significant change in the photoemission yield spectra due to exposure to a dry atmosphere was observed. To gain a better understanding of these results, observations of the change in the photoemission yield spectra caused by the thermal desorption of adsorbed water were also carried out. The results are consistent with those obtained by exposure to a dry atmosphere. Based on the relationship between the photoemission yield and the thickness of the water layer, the time dependence of the change in the thickness was explained by the second-order reaction rate equation.

We report a result of combined in-situ x-ray absorption spectroscopy (XAS) and first-principles calculation study on LiNi1/3Co1/3Mn1/3O2 cathode material, especially focusing on the roles of individual transition metals and oxygen for the battery reactions The theoretical X-ray Absorption Near Edge Structure (XANES) spectra simulations of LixNi1/3Co1/3Mn1/3O2 have been well reproduced experimental in situ XANS spectra, and behaviors of XANES spectral shapes are reasonably explained with electronic structure considerations. Results of such analysis revealed that Ni mainly contribute to the battery-redox-reaction, while Co contribute only at high potential regions, and Mn does not contribute to the reaction.

A flow chemiluminescence (CL) method combined with a liquid-liquid extraction technique is proposed for the indirect determination of antimony in aqueous samples using rhodamine B (RB). In the liquid-liquid extraction process, the antimony(V) chloro-complex anion, [SbCl6]−, was extracted from an aqueous acidic solution into toluene viaion-pair formation with the protonated RBH+ion. Upon mixing the extract with a reversed micellar reagent solution of cetyltrimethylammonium chloride (CTAC) in 1-hexanol-cyclohexane/water (0.60 mol dm−3H2SO4) containing cerium(IV), uptake of the ion-pair by CTAC reversed micelles occurred easily, followed by an oxidation reaction of RB with Ce(IV) in the CL process. The CL signal produced was then measured. Using a flow injection system, the detection limits (DL) of 0.25 μmol dm−3Sb(III) and 0.20 μmol dm−3Sb(V), and linear calibration graphs with dynamic ranges from the respective DLs to 16 μmol dm−3for Sb(III) and Sb(V) were obtained under optimized experimental conditions. The proposed method was successfully applied to a mixture of Sb(III) and Sb(V), where total antimony, Sb(III) + Sb(V), was measured using ceric sulfate as an oxidant to oxidize Sb(III) to Sb(V) prior to extraction, Sb(V) was determined directly without the use of an oxidant, and Sb(III) was calculated by difference.

The charge compensation mechanisms in polycrystalline Pr1-xCaxCoO3-\deltaand Pr1-xSrxCoO3-\deltahere synthesized by the solid-state reaction method have been investigated by analyzing the Pr-L3and Co-K X-ray absorption near-edge structure (XANES) with the aid of first-principles calculations. The valence states of Pr ions in these materials were determined to be trivalent (Pr3+) and independent of the concentration of alkaline-earth ions observed in the Pr-L3XANES profile. The Co-K XANES spectra shifted to the higher-energy side with an increase in alkaline-earth concentration and were examined in detail by first-principles calculations. Using calculated XANES results, we successfully determined that the valence state of Co ions is an intermediate value between 3+ and 4+ and increases with an increase in the concentration of alkaline-earth ions in Pr1-xAxCoO3-\delta(A = Ca, Sr) accompanying oxygen vacancy.

In this paper, we introduce a wearable accelerometer array system and propose a method for analysis of human movements. While many studies of sensor networks have aimed at scalability and/or accuracy, our concept is to introduce “redundancy” in the array to measure movements in human bodies. In particular, we gather data from as many points as possible, more than kinematic degrees of freedom, and then obtain various information by data mining. We developed an accelerometer array system based on our “redundant numbered BSN (rBSN)” concept. It measures 46 channels of 3-axis (15 channels of 6-axis) acceleration data in 1500Hz synchronously. We also evaluate our accelerometer array system in two applications discuss the applicability of our rBSN concept. Specifically, we describe methods to estimate arm stiffness as well as center of gyration of human movement.

We studied interactions of water with OH groups in poly(ethylene‐co‐vinyl alcohol) (EVOH) of the ethylene (Et) compositions of 33, 49, 75, and 89% (mol) using near‐infrared spectroscopy. OH groups are mostly self‐associated and only partly isolated in EVOH matrix, and the fraction of the isolated OH increases with the increase in Et composition. Interactions of water in EVOH were analyzed on the basis of the difference spectrum between the spectrum in a hydrated state and that in the dehydrated state of a sample. The water contained in an EVOH sample with a higher Et content shows a more distinct sharp combination band at about 5285 cm−1 in addition to the main broad band at about 5150 cm−1. The former was assigned to the water that is one‐to‐one hydrogen‐bonded to an isolated OH in the manner as OH::OH2 from the effect of the hydration on the near‐infrared and infrared bands of the isolated OH. The latter was assigned to the water that is multiply hydrogen‐bonded to surrounding associated OH groups and that does not cluster. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2425–2437, 2006

Ethylene vinyl alcohol (EVOH)–based packaging structures were analyzed in terms of both barrier properties and morphological alterations after a retorting process and as functions of ethylene content. From the results, it was found that the samples do have a substantial decrease in oxygen barrier properties and that the kinetics of recovery strongly depends on the copolymer ethylene fraction. A morphological deterioration was also observed as a result of retorting, particularly for packaging structures composed of EVOH copolymers of low ethylene contents. However, the polymer morphology and barrier properties were restored after a dry thermal treatment of the retorted samples. Interestingly, preannealing of copolymers of low ethylene content rendered them more resistant to the retorting process by means of promoting both a more robust crystallinity and a lower water sorption capacity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2192–2202, 2005

The properties of ceramic materials are strongly influenced by the presence of ultradilute impurities (dopants). Near-edge X-ray absorption fine structure (NEXAFS) measurements using third-generation synchotron sources can be used to identify ultradilute dopants, provided that a good theoretical tool is available to interpret the spectra. Here, we use NEXAFS analysis and first-principles calculations to study the local environments of Ga dopants at levels of 10 p.p.m in otherwise high-purity MgO. This analysis suggests that the extra charge associated with substitutional Ga on a Mg site is compensated by the formation of a Mg vacancy. This defect model is then confirmed by positron lifetime measurements and plane-wave pseudopotential calculations. This powerful combination of techniques should provide a general method of identifying the defect states of ultradilute dopants in ceramics.

Structure and orientational behavior of two kinds of segmented poly(urethaneurea)s, SPUUs, having different soft segment molecular weights, were investigated by dynamic infrared absorption dichroism (DIR). DIR is a rheo-optical technique and a powerful tool to study orientational behavior of individual segments on multi-phase polymers under sinusoidal mechanical stimuli. SPUUs, being multi-block copolymers, consist of hard segment domains and soft segment matrix. Analysis of the temperature and frequency dependence of the dynamic strain–dichroic ratio coefficient, L*disclosed the following: (1) both the hard and soft segments are deformed synchronously (in-phase) with respect to applied strain, (2) the Arrhenius plot for the shift factor of L*is composed of two contributions, ß (the glass transition) and ? dispersions (local motions related to methylene sequences). These observed dispersions were consistent with the corresponding mechanical dispersions, and (3) the hard segment of SPUU, having a larger soft segment molecular weight (TM-3), has a higher capability of orientation in response to external strain than that having a smaller soft segment molecular weight (TM-1).

Hydrogen bonds in segmented poly(urethaneurea)s (SPUU) were studied with Fourier transform infrared spectroscopy (FT IR). Absorption curves due to the urethane and urea carbonyl groups were resolved into several peaks by a peak resolving method. Evaluation of individual peak intensity enabled one to estimate the amounts of hydrogen bonds formed with urea and urethane carbonyl groups, referred to as hydrogen bond indices, HUAand HUT, respectively. HUAand HUTwere defined as the ratios of absorbances of hydrogen bonded carbonyl groups to free carbonyl groups, respectively for urea (UA) and urethane (UT) carbonyl groups. It was found that the indices of hydrogen bonds of urethane and urea carbonyl groups were the parameters which represent phase mixing, i.e., dispersion of hard segments in the soft segment matrix, and the cohesive force in the hard segment domain. The variation of the indices of hydrogen bonds with increasing elongation and temperature indicated progress of the phase mixing and reduction of the cohesive force of the hard segment domain.

Measurement of the pituitary height was performed on magnetic resonance (MR) images of 213 subjects with no known or suspected pituitary and/or hypothalamic disorders. Midsagittal, T1-weighted images were used for measurements and mean heights in each age and sex group were obtained. In the 10 to 69 year range, the pituitary heights were greater in females than in males. The groups of 0–9 years of both genders showed the minimum mean pituitary height The maximum of themean height was observed in the 10 to 19 year age groups of both genders. The height gradually decreased with increasing age after age 20 years. There were no subjects with a height of 9.0 mm in females or 8.0 mm in males. There was a marked discrepancy between MR and autopsy findings in the older subjects, probably related to the upward concavity that is often encountered in the aged gland. Because of this concavity, the midsagittal MR measurement will induce underestimation of the whole gland.

Fe-doped hexagonal-structured BaTiO3is synthesized by the conventional solid-state reaction method. The local environment of the Fe ions doped in the synthesized hexagonal BaTiO3is then investigated by X-ray absorption near edge structure (XANES) measurements and first-principles calculations. It is confirmed from the Fe L2,3-edge XANES spectrum that the charge state of the Fe ions in the synthesized specimen is trivalent. By analyzing the Fe K-edge XANES spectrum of the present specimen with the aid of the first-principles calculations, it is found that doped Fe ions are substituted at the Ti site in Ti2O9groups of face-sharing octahedra in hexagonal BaTiO3.

We report a result of combined in-situ x-ray absorption spectroscopy (XAS) and first-principles calculation study on LiNi1/3Co1/3Mn1/3O2cathode material, especially focusing on the roles of individual transition metals and oxygen for the battery reactions The theoretical X-ray Absorption Near Edge Structure (XANES) spectra simulations of LixNi1/3Co1/3Mn1/3O2have been well reproduced experimental in situ XANS spectra, and behaviors of XANES spectral shapes are reasonably explained with electronic structure considerations. Results of such analysis revealed that Ni mainly contribute to the battery-redox-reaction, while Co contribute only at high potential regions, and Mn does not contribute to the reaction.

Classical model of helium atom is numerically studied. The phase space is investigated with several types of configurations. while most of orbits cause autoionization via chaotic transients, three types of tori are found. One type of torus is quantized semiclassically with the EBK scheme. Chaotic motion due to the strong interactions between electrons is always unbounded and leads to autoionization. Complex structure of phase space with tori and unstable autoionizing orbits is studied.