Performance Maintenance of Dye-Sensitized Solar Cells Using a Latent Heat Storage Material

Recently, there has been considerable interest in various renewable energies. Among them, solar cell production has increased markedly because the photovoltaic is a clean and safe power generation method. The dye-sensitized solar cell (DSSC) has attracted much attention as an alternative to silicon solar cells due to lower manufacturing costs and plentiful resources for DSSC production. However, the performance of DSSCs has been limited by their durability and low photoelectric conversion efficiency. Temperature control of DSSCs via phase-change materials (PCMs) is expected to improve performance. In this study, DSSCs were heated or cooled with a heat exchanger copper block that was in contact with a PCM (heptadecane), while being irradiated by a solar simulator light source. The durability and photoelectric conversion efficiency of the DSSC improved under PCM temperature control.     

Symbol emergence in robotics: a survey

Humans can learn a language through physical interaction with their environment and semiotic communication with other people. It is very important to obtain a computational understanding of how humans can form symbol systems and obtain semiotic skills through their autonomous mental development. Recently, many studies have been conducted regarding the construction of robotic systems and machine learning methods that can learn a language through embodied multimodal interaction with their environment and other systems. Understanding human?-social interactions and developing a robot that can smoothly communicate with human users in the long term require an understanding of the dynamics of symbol systems. The embodied cognition and social interaction of participants gradually alter a symbol system in a constructive manner. In this paper, we introduce a field of research called symbol emergence in robotics (SER). SER represents a constructive approach towards a symbol emergence system. The symbol emergence system is socially self-organized through both semiotic communications and physical interactions with autonomous cognitive developmental agents, i.e. humans and developmental robots. In this paper, specifically, we describe some state-of-art research topics concerning SER, such as multimodal categorization, word discovery, and double articulation analysis. They enable robots to discover words and their embodied meanings from raw sensory-motor information, including visual information, haptic information, auditory information, and acoustic speech signals, in a totally unsupervised manner. Finally, we suggest future directions for research in SER.     

Ultra‐high‐resolution 1058‐ppi OLED displays with 2.78‐in size using CAAC‐IGZO FETs with tandem OLED device and single OLED device

We fabricated new 2.78‐in 1058‐ppi organic light‐emitting diode (OLED) displays. The displays used OLED devices with a tandem structure and a single structure and a field effect transistor (FET) using c‐axis aligned crystalline In–Ga–Zn–O (CAAC‐IGZO) for an active layer and employing the 1.5‐µm rule over a glass substrate. Even in the displays with such high resolution exceeding 1000 ppi, crosstalk that was observed in the lower luminance region was suppressed. The displays achieved high color reproducibility and reduced viewing angle dependence.     

Confinement of Long‐Lived Triplet Excitons in Organic Semiconducting Host–Guest Systems

Long‐lived triplet excitons on organic molecules easily deactivate at room temperature because of the presence of thermally activated nonradiative pathways. This study demonstrates long‐lived phosphorescence at room temperature resulting from suppression of the nonradiative deactivation of triplet excitons in conventional organic semiconducting host–guest systems. The nonradiative deactivation pathway strongly depends on the triplet energy gap between the guest emitting molecules and the host matrices. The triplet energy gap required to confine the long‐lived triplet excitons (≈0.5 eV) is much larger than that of conventional host–guest systems for phosphorescent emitters. By effectively confining the triplet excitons, this study demonstrates long‐lived room‐temperature phosphorescence under optical and electrical excitation.     

Effects of microstructure on the R-curve behaviour of sintered silicon nitride

The R-curve behaviour of sintered silicon nitride was investigated by using short bar specimens. The samples were fabricated by sintering at 1700° C for 2 or 8 h in a nitrogen atmosphere, varying the initial contents of the silicon nitride powder. The R-curve was evaluated with a loading and unloading technique to calculateK _R during stable fracture. Steep R-curves were observed in the specimens made from the high initial content powder. Thus, the grainbridging effect behind the crack seems to contribute to the R-curve, because a steep R-curve corresponds to fibrous texture development. ApparentK _c values with an assumption of linear elastic fracture mechanics for the specimens undergoing 8h sintering, are greater than those undergoing 2 h sintering. These results can be attributed to microcracking.     

Partial oxidation of CH4 at low pressure over SiO2 prepared from Si

The oxidation of CH₄ with O₂ at low pressure was carried out over SiO₂ prepared from metal Si. The Si showed only total oxidation activity while the Si partly oxidized to SiO₂ showed high selectivities to CH₃OH and HCHO. The results on SiO₂ prepared from Si were compared with those over commercial silicas. The role of SiO₂ in the CH₄ oxidation was discussed.     

High Catalytic Performance of Fine Particles of Metallic Iron Formed from Limonite in the Decomposition of a Low Concentration of Ammonia

Catalytic NH₃ decomposition with limonite rich in α-FeOOH has been studied as a hot gas cleanup method to remove a low concentration of NH₃ from fuel gas produced in coal gasification. Fine particles of metallic Fe formed from α-FeOOH achieve the almost complete decomposition of 2000 ppm NH₃ to N₂ at 500°C under a high space velocity of 45,000 h⁻¹ and show the stable catalytic performance for 50 h. The predominant catalytic mechanism involving the formation and subsequent decomposition of Fe nitrides may be proposed on the basis of the XRD and TPD results.     

Phase Relationships in the Si3N4–SiO2–Lu2O3 System

Phase relationships in the Si₃N₄–SiO₂–Lu₂O₃ system were investigated at 1850°C in 1 MPa N₂. Only J-phase, Lu₄Si₂O₇N₂ (monoclinic, space group P 2₁/ c , a = 0.74235(8) nm, b = 1.02649(10) nm, c = 1.06595(12) nm, and β= 109.793(6)°) exists as a lutetium silicon oxynitride phase in the Si₃N₄–SiO₂–Lu₂O₃ system. The Si₃N₄/Lu₂O₃ ratio is 1, corresponding to the M-phase composition, resulted in a mixture of Lu–J-phase, β-Si₃N₄, and a new phase of Lu₃Si₅ON₉, having orthorhombic symmetry, space group Pbcm (No. 57), with a = 0.49361(5) nm, b = 1.60622(16) nm, and c = 1.05143(11) nm. The new phase is best represented in the new Si₃N₄–LuN–Lu₂O₃ system. The phase diagram suggests that Lu₄Si₂O₇N₂ is an excellent grain-boundary phase of silicon nitride ceramics for high-temperature applications.     

Strength Retention in Hot-Pressed Si3N4 Ceramics with Lu2O3 Additives after Oxidation Exposure in Air at 1500°C

The effect of oxidation exposure on room-temperature flexural strength was examined in 3.33- and 12.51-wt%-Lu₂O₃-containing hot-pressed Si₃N₄ ceramics exposed to air at 1500°C for up to 1000 h. After oxidation exposure, the room-temperature strength of the ceramics was degraded, and strength retention decreased with time at temperature, dependent on the amount of additive. The retention in room-temperature strength displayed by the two compositions after 1000 h of oxidation exposure was 75%–80%. The degradation in strength was attributed to the formation of new defects at and/or near the interface between the oxide layer and the Si₃N₄ bulk during oxidation exposure.     

(24S)-14α,24-dimethyl-9β,19-cyclo-5α-cholest-25-en-3β-ol: A new sterol and other sterols inMusa sapientum

The structure of a new sterol isolated fromMusa sapientum has been shown by chemical and spectroscopic methods to be (24S)-14α,24-dimethyl-9α,19-cyclo-5α-cholest-25-en-3β-ol. In addition, several known (24S)-24-methyl-Δ²⁵-sterols, their 24-methylene isomers and other sterols (4,4-dimethyl-, 4α-methyl- and 4-demethyl-sterols) together with 3-oxo-4α-methylsteroids were isolated from the plant and identified. The biogenetic implication of these sterols and 3-oxosteroids is discussed.