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Low-dimensional materials have remarkable properties that are distinct from their bulk counterparts. A paradigmatic example is Ising superconductivity that occurs in monolayer materials such as NbSe2 which show a strong violation of the Pauli limit. In monolayers, this occurs due to a combination of broken inversion symmetry and spin-orbit coupling that locks the spins of the electrons out-of-plane. Bulk NbSe2 is centrosymmetric and is therefore not an Ising superconductor. We show that bulk misfit compound superconductors, (LaSe)1.14(NbSe2) and (LaSe)1.14(NbSe2)2, comprised of monolayers and bilayers of NbSe2, exhibit unexpected Ising protection with a Pauli-limit violation comparable to monolayer NbSe2, despite formally having inversion symmetry. We study these misfit compounds using complementary experimental methods in combination with first-principles calculations. We propose theoretical mechanisms of how the Ising protection can survive in bulk materials. We show how some of these mechanisms operate in these bulk compounds due to a concerted effect of charge-transfer, defects, reduction of interlayer hopping, and stacking. This highlights how Ising superconductivity can, unexpectedly, arise in bulk materials, and possibly enable the design of bulk superconductors that are resilient to magnetic fields., Comment: 14 pages, 4 figures, 4 extended data items

Using a new crystal engineering tool, we prepared organic solid-state light-emitting materials that exhibit very bright monomeric emissions. Introducing flexible alkylene bridges into distyrylbenzene (blue fluorescent dye) generated the desired crystal structure in which each dye is isolated in a compact space.

To design ultrabright fluorescent solid dyes, a crystal engineering strategy that enables monomeric emission by blocking intermolecular electronic interactions is required. We introduced propylene moieties to distyrylbenzene (DSB) as bridges between the phenyl rings either side of its C=C bonds. The bridged DSB derivatives formed compact crystals that emit colors similar to those of the same molecules in dilute solution, with high quantum yields. The introduction of flexible seven-membered rings to the DSB core produced moderate distortion and steric hindrance in the DSB π-plane. However, owing to this strategy, it was possible to control the molecular arrangement with almost no decrease in the crystal density, and intermolecular electronic interactions were suppressed. The bridged DSB crystal structure differs from other DSB derivative structures; thus, bridging affords access to novel crystalline systems. This design strategy has important implications in many fields and is more effective than the conventional photofunctional molecular crystal design strategies.

We have developed phenomenological turbulent effects with one-dimensional (1D) simulation based on Reynolds decomposition. Using the method, we have conducted a systematic study of 320 models changing progenitor mass, mixing-length parameter, and diffusion coefficients for internal energy, turbulent energy, and electron fraction. With employed turbulent effects, supernova explosion can be achieved even in 1D geometry. We find that smaller diffusive transport on the internal energy makes the shock revival faster and explosion energy larger in contrast to the prediction of the previous study. The smaller diffusion keeps the negative entropy gradients and enhances the turbulent pressure, hindering mass accretion in the gain region. The progenitor dependence of explodability is also investigated in the mixing-length parameter plane and diffusion coefficients plane. These simulations would help understand the role of turbulence in core-collapse supernovae., Comment: 18 pages, 16 figures, submitted to ApJ

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学位の種別: 論文博士, 審査委員会委員 : （主査）東京大学教授 柳本 潤, 東京大学教授 泉 聡志, 東京大学准教授 長藤 圭介, 東京大学准教授 南部 将一, 東京工業大学准教授 中田 伸生

Twenty years ago, the concept of aggregation‐induced emission (AIE) was proposed, and this unique luminescent property has attracted scientific interest ever since. However, AIE denominates only the phenomenon, while the details of its underlying guiding principles remain to be elucidated. This minireview discusses the basic principles of AIE based on our previous mechanistic study of the photophysical behavior of 9,10‐bis(N,N‐dialkylamino)anthracene (BDAA) and the corresponding mechanistic analysis by quantum chemical calculations. BDAA comprises an anthracene core and small electron donors, which allows the quantum chemical aspects of AIE to be discussed. The key factor for AIE is the control over the non‐radiative decay (deactivation) pathway, which can be visualized by considering the conical intersection (CI) on a potential energy surface. Controlling the conical intersection (CI) on the potential energy surface enables the separate formation of fluorescent (CI:high) and non‐fluorescent (CI:low) molecules [control of conical intersection accessibility (CCIA)]. The novelty and originality of AIE in the field of photochemistry lies in the creation of functionality by design and in the active control over deactivation pathways. Moreover, we provide a new design strategy for AIE luminogens (AIEgens) and discuss selected examples., What is essential in the aggregation‐induced emission (AIE) mechanism? This question is addressed by using the photophysical processes associated with 9,10‐bis(N,N‐dialkylamino)anthracene as a case study. The AIE phenomenon requires control of the non‐radiative decay (deactivation) pathway, that is, controlling the conical intersection (CI) on the potential energy surface enables the formation of fluorescent molecules (CI high) and non‐fluorescent (CI low) molecules separately.

In recent years, all-solid-state batteries (ASSBs) have been attracting attention as the next generation batteries for electric vehicles, energy storage systems, etc. Despite the growing interest, there are still many challenges faced in the commercial use of ASSBs. One of the biggest issues is the internal resistance, especially generated at the interface between solid electrolyte and electrode. The internal resistance at the interface limits the charge-discharge cycling performances. In order to solve this issue, it is necessary to examine the chemical and physical interactions at the interface. In this study, we have performed a detailed characterization of a LiPON/LiCoO2 interface using time-of-flight secondary ion mass spectrometry, x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and low-energy inverse photoelectron spectroscopy to obtain information on chemical species, chemical compositions, chemical states, and energy band diagrams. These powerful techniques have revealed that an interlayer between LiPON and LiCoO2 was formed due to the temperature rise during the manufacturing process. The temperature rise caused a change of the LiPON network structure and stimulated Co reduction in the LiCoO2 layer near the interface. Energy band diagram analysis suggests that the electron diffusion from LiPON to LiCoO2 may have triggered the reduction of Co. We concluded that the chemical changes that occur at the interface caused an increase in interfacial impedance. Preventing the chemical reduction of Co would be a key to minimize the internal resistance. In this article, the detailed chemical interactions between the LiPON and LiCoO2 layers will be discussed.

In recent years, speech synthesis technology has been developed, but the method of expressing emotions with synthesized speech was one of the issue. Therefore, in the latest speech synthesis technology, a method for expressing emotion by synthesized speech continues to be developed. For example, as one of them, it is a method of changing the physical values such as the height of the sound and the speaking speed, reproducing emotions such as joy and anger, and reading out the text. Emotional expression of synthesized speech is to reproduce human emotions by physically changing the height of sound, speech speed, intonation, and the like. However, we do not hear much comparison between synthesized speech expressing emotion and human one. Therefore, in this study, we conducted a control experiment on whether there is a difference between synthesized speech expressing emotion and human speech. In this control experiment method, two sounds, one synthesized by using one of the speech synthesis software and one recorded with human speech, are visualized as speech signals, and the differences that can be analyzed from these characteristics are listed. In this research, the speech signal is displayed as a waveform, frequency analysis and so on. As a result, various speech features were able to be grasped. For example, in the voice of anger by humans, as the anger becomes stronger, the strength of the vowel becomes stronger and the overall volume increases, it turned out that the synthesized speech also reproduced by imitating the feature.

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Translation title: Reliability Control Tecnique for Manned Space Systems Acquired in the Development of KIBO, 資料番号: AA0061925004, レポート番号: JAXA-SP-12-015

On wearable devices where an MCU primarily remains in an idle state, keeping the MCU in a deep sleep mode during idle periods can lead to significant power reduction. Since the deep sleep mode has a relatively high wake-up overhead, one of the effective techniques for power reduction is to decrease the wake-up frequency of the MCU. Meanwhile, due to the recent trend of increasing the number of sensors embedded in wearable devices, the MCU must wake up more frequently for data acquisitions from the sensors. This indicates an increase in power consumption caused by frequent wakeups. In this paper, we propose a new method to achieve power reduction of the MCU for wearable applications. The applications acquire data periodically from multiple sensors. Our proposed method achieves low power consumption by gathering the scattered data acquisitions of the sensors and decreasing the wake-up frequency. The experimental result shows that the proposed method achieved an 8.5–31% power reduction in the MCU.

System Dependence Graph (SDG) is a graph representation which shows dependencies among statements / expressions in a design. In this paper, we propose a new HW/SW co-design methodology based on SDG. In our method, any combination of C / C++ / SpecC descriptions is acceptable as input designs so that design functions can be specified flexibly. First, the input descriptions are analyzed and verified with static but partially dynamic program checking methods by traversing SDG. With those methods, large descriptions can be processed. Next, those designs are divided into HW and SW parts. In this step, SDGs are fully utilized to insert parallelism into the designs, and it enables flexible HW/SW partitioning. The HW parts are further optimized and then converted into RTL descriptions by existing behavioral synthesis tools. Finally, the generated RTL descriptions together with the SW parts are compared to the original descriptions in order to make sure that they are logically equivalent. Also, designerspecified properties may be model checked with these final design descriptions. Such formal verifications can be realized by translating those descriptions into Finite State Machine (FSM) type representations and existing formal verifiers. We show two case studies with practical examples to demonstrate the usefulness of our approach.

Topochemistry enables step-by-step conversions of solid-state materials often leading to metastable structures that retain initial structural motifs. Recent advances in this field revealed many examples where relatively bulky anionic constituents were actively involved in redox reactions during (de)intercalation processes. Such reactions are often accompanied by anion-anion bond formation, which heralds possibilities to design novel structure types disparate from known precursors, in a controlled manner. Here we present the multistep conversion of layered oxychalcogenides Sr2MnO2Cu1.5Ch2 (Ch = S, Se) into Cu-deintercalated phases where antifluorite type [Cu1.5Ch2]2.5- slabs collapsed into two-dimensional arrays of chalcogen dimers. The collapse of the chalcogenide layers on deintercalation led to various stacking types of Sr2MnO2Ch2 slabs, which formed polychalcogenide structures unattainable by conventional high-temperature syntheses. Anion-redox topochemistry is demonstrated to be of interest not only for electrochemical applications but also as a means to design complex layered architectures.