Yuya Sasaki 교수

The particle-size dependence of frequencies and dampings of optical phonons is studied from analyses of Raman-scattering and infrared-absorption spectra of SiC small particles. The particle size ranges from a few nanometers to more than 1 \ensuremath{\mu}m. The measured spectra are explained qualitatively in terms of a model of a core plasmon and a carrier-free layer on the surface (shell) of the particles, provided that their sizes are larger than about 30 nm. Here we use Mie's scattering equat

The Internet of Things (IoT) has become widespread around the world. Since a large number of diverse devices, such as vehicles, household electrical appliances, smart phones, and environmental sensors are connected to the Internet, we can obtain a large volume of diverse IoT data, known as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IoT big data</i> . The generation of IoT big data means that efficient analytic systems are needed for many app

We have studied phonon states of Ge small particles by Raman scattering resonating with the ${\mathit{E}}_{1}$\ensuremath{\sim}${\mathit{E}}_{1}$+${\mathrm{\ensuremath{\Delta}}}_{1}$ gaps. Those particles are prepared by evaporation in Ar gas atmosphere and their sizes range from about 2 through 30 nm. Since the electronic transition energy depends on the particle size as a result of confinement of the electron and hole in the particle, we can selectively excite the particle with a specific diam

Continuous-wave (CW) terahertz radiation based on nonlinear difference frequency mixing (DFM) of two laser lights outputs is demonstrated. The surface-emitting method generated THz frequency radiation in the perpendicular direction of incident laser light by quasi-phase-matching. Periodically poled lithium niobate (PPLN) served as the nonlinear material for this surface-emitting method. In this case, two diode laser wavelengths of 1.5 µm can be applied as DFM sources, within the range of telecom

Advancements in large language models (LLMs) are transforming software engineering through innovative prompt engineering strategies. By analyzing prompt-driven enhancements across key software engineering tasks, we present a sys-tematic literature review and a pioneering taxonomy elucidating the practical applications of prompt engineering in software engineering. Our taxonomy offers a foundational framework that clarifies the roles of prompt engineering and measures its impact, thereby guiding

In mobile ad hoc networks (MANETs), to acquire only necessary data items, it is effective that each mobile node retrieves data items using a top-k query, in which data items are ordered by the score of a particular attribute and the query-issuing mobile node acquires data items with k highest scores. In this paper, we propose a query processing method for top-k query for reducing traffic and also keeping high accuracy of the query result. In this method, each mobile node constructs a histogram f

The hypertext transfer protocol (HTTP) has been widely used as a communication protocol for Internet access. However, for Internet of things (IoT) communication, which is expected to grow in the future, HTTP requires a large overhead and cannot provide efficiency. In order to solve this problem, lightweight communication protocols for IoT have been discussed. In this paper, we clarify some problems of HTTP for IoT and propose MQ telemetry transport (MQTT), which is a promising candidate for the

Vehicular ad hoc networks (VANETs) have been attracting increasing research interests for the past decade. To address the routing problem, many protocols have been proposed in the past several years. Routing protocols for VANETs, mostly based on the ideas of “Geographical Routing” (or geo-routing for short), typically have nodes periodically broadcast one-hop beacon messages to reveal their positions to neighbors. Nevertheless, packet loss and thus deterioration of routing performance in these p

Arc-fusion splicing of 2.1 km-long single-polarisation fibres with stress-induced birefringence is performed using mode-locked YAG laser pulses. By monitoring the pulse shapes due to the polarisation dispersion, alignment for the parallel or the crossprincipal axes of the core refractive-index ellipsoid is easily realised.

The microscopic structure and formation processes of porous Si layers (PSLs) have been studied by infrared absorption and Raman scattering. How the concentration of HF used during formation affects the vibrational spectra of PSLs has been examined. The IR spectra of as-anodized PSL in the Si-Hx vibration region are quite similar to those of Si(111) or (100) surfaces etched in HF solutions of pH∼2. The amount of dihydrogen adsorbed on the surface increases for lower HF concentrations relative to

The absorption coefficient, reflectivity and electroreflectance of the layer compound gallium selenide in the photon energy region 3 eV to 4.2 eV were measured at room temperature and at 90 K. It is found that there exist four structures at 3.36 eV, 3.70 eV, 3.9 eV and 4.1 eV at 90 K. A tentative assignment of the types of critical points is made.

The binding centers of the indirect bound excitons in $\ensuremath{\epsilon}\ensuremath{-}\mathrm{G}\mathrm{a}\mathrm{S}\mathrm{e}$ are identified from the magnetoluminescence up to 10 T at 4.2 K and from the temperature dependence of the photoluminescence spectra in the temperature range from 4.2 to 25 K. The two different kinds of experiments lead to the same conclusion that six indirect bound-exciton lines in the photon energy range of 2.0785 to 2.0992 eV at 4.2 K are due to the radiative rec