Thermal comfort is an essential environmental factor related to quality of life and work effectiveness. We assessed the feasibility of wrist skin temperature monitoring for estimating subjective ...thermal sensation. We invented a wrist band that simultaneously monitors skin temperatures from the wrist (i.e., the radial artery and ulnar artery regions, and upper wrist) and the fingertip. Skin temperatures from eight healthy subjects were acquired while thermal sensation varied. To develop a thermal sensation estimation model, the mean skin temperature, temperature gradient, time differential of the temperatures, and average power of frequency band were calculated. A thermal sensation estimation model using temperatures of the fingertip and wrist showed the highest accuracy (mean root mean square error RMSE: 1.26 ± 0.31). An estimation model based on the three wrist skin temperatures showed a slightly better result to the model that used a single fingertip skin temperature (mean RMSE: 1.39 ± 0.18). When a personalized thermal sensation estimation model based on three wrist skin temperatures was used, the mean RMSE was 1.06 ± 0.29, and the correlation coefficient was 0.89. Thermal sensation estimation technology based on wrist skin temperatures, and combined with wearable devices may facilitate intelligent control of one's thermal environment.
The effects of porosity on the electrical and thermal conductivities of porous SiC ceramics, containing Y2O3–AlN additives, were investigated. The porosity of the porous SiC ceramic could be ...controlled in the range of 28–64 % by adjusting the sacrificial template (polymer microbead) content (0–30 wt%) and sintering temperature (1800–2000 °C). Both electrical and thermal conductivities of the porous SiC ceramics decreased, from 7.7 to 1.7 Ω−1 cm−1 and from 37.9 to 5.8 W/(m·K), respectively, with the increase in porosity from 30 to 63 %. The porous SiC ceramic with a coarser microstructure exhibited higher electrical and thermal conductivities than those of the ceramic with a finer microstructure at the equivalent porosity because of the smaller number of grain boundaries per unit volume. The decoupling of the electrical conductivity from the thermal conductivity was possible to some extent by adjusting the sintering temperature, i.e., microstructure, of the porous SiC ceramic.
The effects of the polytype of SiC starting powders on the thermal, electrical, and mechanical properties of pressureless sintered SiC ceramics with a new additive system (6.5vol% Y2O3-Sc2O3-AlN) ...were investigated. Powder mixtures prepared from α- or β-SiC powders were sintered at 1950°C for 6h in a nitrogen atmosphere without an applied pressure. We found that both specimens could be sintered to >96% of the theoretical density without an applied pressure. The SiC ceramic fabricated from β-SiC powders showed lower electrical resistivity, higher thermal conductivity, and better mechanical properties than that from α-SiC powders. The flexural strength, fracture toughness, hardness, electrical resistivity and thermal conductivity values of the SiC ceramics fabricated from β-SiC powders were 520MPa, 5.1MPam1/2, 25.0GPa, 6.7×10−1Ωcm and 110 Wm−1K−1 at room temperature, respectively. The new additive system achieved the highest thermal conductivity in pressureless liquid-phase sintered SiC ceramics.
CoFe
2
O
4
has been attracting attention for its ferrimagnetism applicable to spin transfer, resonance imaging, drug delivery etc. CoFe
2
O
4
thin films were synthesized on Si(100) substrates by ...using a sol–gel deposition process. The CoFe
2
O
4
specimen produced by post-annealing in air at 800 °C showed flat surface and polycrystalline grains with no secondary phase. The specimen exhibited magnetic hysteresis curve with magnetization up to 415 emu/cm
3
and coercivity of 1.7 kOe. Such a large magnetization implies migration of a number of Co
2+
ions from octahedral to tetrahedral sites of the spinel lattice. The distribution of Co
2+
ions among tetrahedral and octahedral sites of CoFe
2
O
4
was estimated by curve-fitting analysis on the Raman scattering spectrum of the specimen. The result suggests 30% of the Co
2+
ions residing in the tetrahedral sites. The coexistence of Co
2+
ions in both tetrahedral and octahedral sites of CoFe
2
O
4
was also detectable by using Co 2
p
X-ray photoelectron spectroscopy.
The CoFe
2
O
4
thin-film specimen deposited on Si(100) substrate through a sol–gel process exhibited surface flatness and phase-pure polycrystalline grains. The specimen showed magnetic hysteresis curve with magnetization up to 415 emu/cm
3
, coercivity of 1.7 kOe and remnant magnetization of 170 emu/cm
3
. The observed magnetization exceeded theoretical value expected for pure inverse spinel CoFe
2
O
4
and can be explained in terms of migration of a fraction of Co
2+
ions from octahedral to tetrahedral sites of the spinel lattice. The inversion parameter of the CoFe
2
O
4
specimen was estimated to be 0.70 through a curve-fitting on its Raman scattering spectrum. The curve-fitting analysis on Co 2
p
XPS spectrum of the specimen turned out to be supportive of the Raman analysis.
Highlights
CoFe
2
O
4
thin films with high crystalline quality have been fabricated on Si(100) substrates by using a sol–gel technique and post-annealing in air at 800 °C.
Thin-film CoFe
2
O
4
specimen exhibits magnetization (415 emu/cm
3
) that is larger than theoretical value (380 emu/cm
3
) expected for pure inverse spinel CoFe
2
O
4
.
The enhanced magnetization of CoFe
2
O
4
is ascribed to the migration of Co
2+
ions to the tetrahedral sites of the spinel lattice.
The inversion parameter of CoFe
2
O
4
is estimated to be 0.70 through a curve-fitting analysis on the Raman scattering spectrum of the specimen.
Defects of cyclotrimethylene trinitramine (RDX) crystals prepared by cooling crystallization in various mixed solvents were studied. A normal RDX and a reduced sensitivity RDX were compared with ...recrystallized RDX crystals in terms of thermal analysis by differential scanning calorimetry, matching refractive index, scanning electron microscopy, bulk density, and gas chromatography. Activation energy was calculated by thermal analysis using Kissinger’s plot and correlated with supersaturation, bulk density, and inclusion fraction. The quality of the RDX crystallized in various solvents was examined by the activation energy, which is expressed as a function of the supersaturation. Formation of crystals with smooth and flawed faces can be interpreted by the relationship between supersaturation and activation energy, which enables discrimination between a reduced sensitivity RDX and normal RDX. In high supersaturation, nucleation of new layers occurs at the edges and corners of the crystal, and layered growth becomes dominant. The cracks are characterized by the overlapping of layers at the crystal faces.
Linear alkyl benzene-based liquid scintillators (LSs) have been extensively used as targets for neutrino detectors in recent decades owing to their environmentally friendly properties, high light ...yield, and cost efficiency. Neutrino events are typically reconstructed from scintillation events observed by photomultiplier tubes (PMTs) attached to the detector. A comprehensive understanding of the LS response is required for interpreting reconstructed neutrino events during detector operation. In this study, we investigate the properties of scintillation events such as light yield, waveform, and wavelength shift of the emitted scintillation light at various concentrations of fluor dissolved in the LS. The light yield, waveform, and wavelength shift exhibit a nonlinear relationship with fluor concentration, complicating the determination of fluor concentration from the observed characteristics of the scintillation events. We employ a convolutional neural network (CNN) to model this nonlinear relationship between fluor concentration and LS properties. The CNN learns the distinctive features of the scintillation events from observed waveforms and the relative ratio of the light yield below 425 nm to the total light yield detected by a PMT at different fluor concentrations. The trained CNN was able to distinguish the scintillation events with different 2,5-diphenyloxazole and 1,4-bis(2-methylstyryl)benzene concentrations according to the observed waveform and relative wavelength shift. The classified scintillation events for each LS sample exhibited clear features for the different LS concentrations, emphasizing the discriminative capability of the trained CNN. This research presents the first demonstration of LS fluor concentration discrimination using machine-learning techniques in PMT-based detectors.
Liquid scintillators are extensively employed as targets in neutrino experiments and in medical radiography. Perovskite nanocrystals are recognized for their tunable emission spectra and high ...photoluminescence quantum yields. In this study, we investigated the feasibility of using perovskites as an alternative to fluor, a substance that shifts the wavelengths. The liquid scintillator candidates were synthesized by doping perovskite nanocrystals with emission wavelengths of 450, 480, and 510 nm into fluor PPO with varying nanocrystal concentrations in a toluene solvent. The several properties of the perovskite nanocrystal-doped liquid scintillator were measured and compared with those of a secondary wavelength shifter, bis-MSB. The emission spectra of the perovskite nanocrystal-doped liquid scintillator exhibited a distinct monochromatic wavelength, indicating energy transfer from PPO to the perovskite nanocrystals. Using a 60Co radioactive source setup with two photomultiplier tubes (PMTs), the light yields, pulse shape, and wavelength shifts of the scintillation events were measured. The light yields were evaluated based on the observed Compton edges from γ-rays, and compared across the synthesized samples. A decrease (or increase) in area-normalized PMT pulse height was observed at higher perovskite nanocrystal (or PPO) concentrations. The results demonstrated the sufficient potential of perovskite nanocrystals as an alternative to traditional wavelength shifters in a liquid scintillator.
Kinetics of anti‐solvent crystallization of HNIW polymorphs were studied using in situ Raman spectroscopy and focused beam reflectance measurement (FBRM). Crystal polymorphs and supersaturation were ...monitored in situ by Raman spectroscopy. Crystal counts and crystal size were monitored by FBRM during anti‐solvent crystallization. The addition rate of the anti‐solvent affected the polymorph transformation, the first polymorph of the crystals, and supersaturation. At a wide range of addition rate, the unstable form, β‐form, was detected and then transformed to the stable form, ϵ‐form. By controlling the concentration and rate of addition, the stable form, ϵ‐form was only nucleated and grown without transformation. This process depended on the supersaturation and affected polymorphic transformation, concentration, nucleation rate, and growth rate, which were simultaneously monitored by Raman spectroscopy and FBRM.
Neutrinos are difficult to detect because they weakly interact with matter, making their properties least known. The response of the neutrino detector depends on the optical properties of the liquid ...scintillator (LS). Monitoring any characteristic changes in the LS helps to understand the temporal variation of detector response. In this study, a detector filled with LS was used to study the characteristics of the neutrinos detector. We investigated a method to distinguish the concentrations of PPO and bis-MSB, which are fluors added to LS, through a photomultiplier tube (PMT) acting as an optical sensor. Conventionally, it is very challenging to discriminate the flour concentration dissolved in LS. We employed the information of pulse shape and PMT coupled with the short-pass filter. To date, no literature report on a measurement using such an experimental setup has been published. As the concentration of PPO was increased, changes in the pulse shape were observed. In addition, as the concentration of bis-MSB was increased, a decrease in the light yield was observed in the PMT equipped with the short-pass filter. This result suggests the feasibility of real-time monitoring of LS properties, which are correlated with the fluor concentration, using a PMT without extracting the LS samples from the detector during the data acquisition process.
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