Tomoko Takahashi 교수

This paper reviews methods to compensate for matrix effects and self-absorption during quantitative analysis of compositions of solids measured using Laser Induced Breakdown Spectroscopy (LIBS) and their applications to in-situ analysis. Methods to reduce matrix and self-absorption effects on calibration curves are first introduced. The conditions where calibration curves are applicable to quantification of compositions of solid samples and their limitations are discussed. While calibration-free

This study describes a method to quantify the chemical composition of deep-sea hydrothermal deposits in situ using laser-induced breakdown spectroscopy (LIBS). Partial least squares (PLS) regression analysis is applied to spectra obtained using a long laser pulse with a duration of 150 ns. The number of measurements needed to address the spatial heterogeneity of samples is determined through high-resolution mapping of the elemental distribution in rock samples. PLS applied to laboratory measured

Long-ns-duration, single pulse laser-induced breakdown spectroscopy (LIBS) is known to be an effective method to observe well resolved spectra from samples immersed in water at high hydrostatic pressures. The aim of this study is to investigate whether the signals obtained using this method are suitable for quantitative analysis of chemical composition. Six certified brass alloys consisting of copper (Cu), zinc (Zn) and lead (Pb) were measured underwater using a laser pulse of duration 250 ns, a

A noncontact method to identify sparsely distributed plastic pellets is proposed by integrating holography and Raman spectroscopy in this study. Polystyrene and poly(methyl methacrylate) resin pellets with a size of 3 mm located in a 20 cm water channel were illuminated using a collimated continuous wave laser beam with a diameter of 4 mm and wavelength of 785 nm. The same laser beam was used to take a holographic image and Raman spectrum of a pellet to identify the shape, size, and composition

Microplastic pollution is an urgent global issue. While spectroscopic techniques have been widely used for the identification of plastics collected from aquatic environments, these techniques are often labor-intensive and time-consuming due to sample collection, preparation, and long measurement times. In this study, a method for the two-dimensional detection and classification of flowing microplastic and organic biotic particles with high spatial and temporal resolutions has been proposed based

The effects of pressure on double-pulse laser-induced breakdown spectroscopy (LIBS) for analysis of the composition of solids submerged in water have been investigated. It has been found that while an increase in water pressure results in an overall reduction in plasma temperature and increased broadness in the observed spectra, analytically useful spectra can be observed up to 5 MPa (50 atm). The results suggest that double-pulse laser-induced breakdown spectroscopy may be suitable for in situ

This study describes a method to quantify the composition of brass alloys submerged in water using laser-induced plasmas. Principal component regression (PCR) analysis and partial least squares (PLS) regression analysis are applied to spectral measurements of plasmas generated using a long-ns duration pulse. The non-linear effects of excitation temperature fluctuations on the signals are treated as systematic errors in the analysis. The effect of these errors on the analytical performance is eva

Effects of different parameters regarding partial least squares (PLS) regression analysis are investigated for quantitative analysis of water-submerged brass samples. The concentrations of Cu and Zn in various brass alloys were quantified using PLS, and the performance after different signal processing steps (normalization, smoothing, and background subtraction) and database segmentation by excitation temperature is compared. In addition, the effects of averaging numbers on the results are exami

Supercritical and liquid CO2 (sc-/liq-CO2) emitted from deep-sea hydrothermal vents create a unique dry environment distinct from seawater and hydrothermal fluids, whose physicochemical characteristics could play an important role in the ocean biogeochemical cycles of the present Earth and even in the prebiotic chemical evolution of the early Earth. While previous studies attempted to sample and analyze sc-/liq-CO2 in several hydrothermal fields, the sampling and analysis without seawater contam

We have developed a method to combine morphological and chemical information for the accurate identification of different particle types using optical measurement techniques that require no sample preparation. A combined holographic imaging and Raman spectroscopy setup is used to gather data from six different types of marine particles suspended in a large volume of seawater. Unsupervised feature learning is performed on the images and the spectral data using convolutional and single-layer autoe

The aim of this paper is to investigate the application of Laser-Induced Breakdown Spectroscopy (LIBS) to qualitatively analyze the composition of various seafloor rock samples in seawater. Well-resolved emission spectra of submerged samples were achieved by using a long laser pulse of duration 250 ns. It was found that the main elements in each rock sample could be successfully identified both in pure water and in seawater. When comparing the measurements made in pure water and in seawater, som

Digital holography is a useful tool to image microscopic particles. Reconstructed holograms give high-resolution shape information that can be used to identify the types of particles. However, the process of reconstructing holograms is computationally intensive and cannot easily keep up with the rate of data acquisition on low-power sensor platforms. In this work, we explore the possibility of performing object clustering on holograms that have not been reconstructed, i.e., images of raw interfe

A new package structure and technology for the next generation of embedded-die package named as WFOP™ (Wide panel Fan-Out Package) was developed. It's a facedown mounting type, using metal plate as the base plate of its redistributed layer. Manufacturing is done not in wafer scale, but in large scale panel substrate. The structure, process, reliability results, and some performance are introduced. The package assembly technology for WFOP is using die-embedding method. So the technology is also a

The aim of this study is to investigate the application of Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS) calculations, to determine the composition of metals and minerals submerged in seawater using a long-pulse laser. The compositions of six different brass standard samples submerged in seawater calculated using CF-LIBS showed good agreement with their certified values. For analysis of minerals, we demonstrate the application of CF-LIBS calculations for classification of hydro

Suspended particles in the ocean play an important role in global nutrient cycles. In this paper, a novel technique for the non-contact fast identification of marine particles is reported. An integrated method of digital holography and Raman spectroscopy aiming at in-situ continuous monitoring of marine particles, particularly in the deep sea where the density of particles is extremely low, is proposed. A particle located in a 20 cm water channel was illuminated using a collimated continuous wav