Spectral Attenuation Coefficient Research Articles

Measurements of the inherent optical properties of aqueous suspensions of microplastics

AbstractLibraries of inherent optical properties (IOPs) of microplastics are sparse, yet they are essential for the development of optical techniques to detect and quantify microplastics in the ocean. In this study, we describe our results and technique for the measurement of the IOPs of microplastic suspensions generated from commonly utilized plastics. The measurements included angle‐resolved polarized light scattering, and spectral absorption and beam attenuation coefficients. We also performed ancillary characterization of particle properties, including size distribution, shape, and mass concentration of suspended matter. We observed several unique optical characteristics regarding absorption, scattering, and polarization properties compared with typical marine particle assemblages. We show that these results are useful for radiative transfer simulations as well as the potential development of novel plastic detection techniques from above‐ or in‐water optical measurements.

A fjord with a land-terminating glacier: Meltwater, bio-optics, particulate matter, nutrients, phytoplankton species, and primary production in west Greenland

Land-terminating glaciers and submarine melting of marine-terminating glaciers are significant features in Arctic regions and are foreseen to become more frequent as marine-terminating glaciers ultimately develop into a land-terminated state. A transition driven by the continuous rise in Arctic air temperatures, and emphasizes the importance of studies of land-terminating glaciers their bio-optical properties and biogeochemistry. Kangerlussuaq in west Greenland with a land-terminating glaciers and was selected for this study. During a research cruise we measured spectral and PAR attenuation, particulate matter concentrations, salinity, nutrient concentrations, Chla, and phytoplankton species composition, along a transect from river outlet to open marine waters. Results showed that surface waters in Kangerlussuaq were strongly influenced by meltwater with low salinities, high particulate matter concentrations, high PAR and spectral light attenuation coefficients, and low nutrient concentrations. Spectral composition was also affected by the particulate matter. PAR photic depths varied between 4 and 9 m dependent on particulate matter concentrations. There was a decrease with distance from outlet in silicate concentrations, and opposite for phosphate, which increased significantly from river outlet to the marine. Phytoplankton species number (42) and diversity were high at the marine station but low (3) in turbid waters dominated by the diatom Skeletonema costatum in high numbers. A meltwater plume covered about 50 % of the Kangerlussuaq at average discharges in early August. Primary production was quantified with a simple model based on light attenuation coefficients, and showed a near exponential decrease in production with increase in attenuation.

Spektral'nyye svyazi gidroopticheskikh kharakteristik v pribrezhnykh vodakh Yuzhnogo berega Kryma

The article studies interrelations of the beam attenuation coefficient in different spectrum regions and spectral relations of beam attenuation coefficient to the Secchi depth in the coastal waters of the South Coast of Crimea. The data were used of in situ optical measurements obtained in 2008–2014 from a stationary oceanographic platform installed in the coastal waters of the South Coast of Crimea near the village of Katsiveli. According to the measurement data the relation was determined of the beam attenuation coefficient in eight parts of the spectrum in the wavelength range of 416–640 nm to the Secchi depth, which varies from 6 m to 17.5 m. Spectral distributions of the beam attenuation coefficient at different Secchi depths in coastal and deep sea waters were compared. As a result, it is concluded that the relationships between the spectral attenuation coefficient and the Secchi depth in coastal waters are not applicable to deep sea waters. It is shown that the feature of such equations in coastal waters is related to the higher concentration of fine suspended matter in them. Intercorrelation parameters were calculated of beam attenuation coefficients in different spectrum regions in coastal waters. High correlation coefficients make it possible to reconstruct distribution of the attenuation coefficient in a wide spectral range based on measurements at one wavelength in any spectrum region. The optimal spectral region to measure the beam attenuation coefficient is 468–527 nm.

Spectral attenuation coefficients from measurements of light transmission in bare ice on the Greenland Ice Sheet

Abstract. Light transmission into bare glacial ice affects surface energy balance, biophotochemistry, and light detection and ranging (lidar) laser elevation measurements but has not previously been reported for the Greenland Ice Sheet. We present measurements of spectral transmittance at 350–900 nm in bare glacial ice collected at a field site in the western Greenland ablation zone (67.15∘ N, 50.02∘ W). Empirical irradiance attenuation coefficients at 350–750 nm are ∼ 0.9–8.0 m−1 for ice at 12–124 cm depth. The absorption minimum is at ∼ 390–397 nm, in agreement with snow transmission measurements in Antarctica and optical mapping of deep ice at the South Pole. From 350–530 nm, our empirical attenuation coefficients are nearly 1 order of magnitude larger than theoretical values for optically pure ice. The estimated absorption coefficient at 400 nm suggests the ice volume contained a light-absorbing particle concentration equivalent to ∼ 1–2 parts per billion (ppb) of black carbon, which is similar to pre-industrial values found in remote polar snow. The equivalent mineral dust concentration is ∼ 300–600 ppb, which is similar to values for Northern Hemisphere warm periods with low aeolian activity inferred from ice cores. For a layer of quasi-granular white ice (weathering crust) extending from the surface to ∼ 10 cm depth, attenuation coefficients are 1.5 to 4 times larger than for deeper bubbly ice. Owing to higher attenuation in this layer of near-surface granular ice, optical penetration depth at 532 nm is 14 cm (20 %) lower than asymptotic attenuation lengths for optically pure bubbly ice. In addition to the traditional concept of light scattering on air bubbles, our results imply that the granular near-surface ice microstructure of weathering crust is an important control on radiative transfer in bare ice on the Greenland Ice Sheet ablation zone, and we provide new values of flux attenuation, absorption, and scattering coefficients to support model development and validation.

Attenuation of Ocean Surface Waves in Pancake and Frazil Sea Ice Along the Coast of the Chukchi Sea

AbstractAlaskan Arctic coastlines are protected seasonally from ocean waves by the presence of coastal and shorefast sea ice. This study presents field observations collected during the autumn 2019 freeze up near Icy Cape, a coastal headland in the Chukchi Sea of the Western Arctic. The evolution of the coupled air‐ice‐ocean‐wave system during a 4‐day wave event was monitored using drifting wave buoys, a cross‐shore mooring array, and ship‐based measurements. The incident wavefield with peak period of 2.5 s was attenuated by coastal pancake and frazil sea ice, reducing significant wave height by 40% over less than 5 km of cross‐shelf distance spanning water depths from 13 to 30 m. Spectral attenuation coefficients are evaluated with respect to wave and ice conditions and the proximity to the ice edge. Attenuation rates are found to be three times higher within 500 m of the ice edge, relative to values farther in the ice cover. Attenuation coefficients are in the range of 〈2.3, 2.7〉x10‐3 m−1, and follow a power‐law dependence on frequency.

Geometry-dependent modal field properties of metal-rod-array-based terahertz waveguides

One terahertz (THz) waveguide based on the metal rod array (MRA) structure is numerically demonstrated in 0.1–1 THz, including the fundamental and high-order transverse magnetic (TM) modes. The high-order TM-mode THz waves are strictly confined inside the MRA structure and are thus sensitive to the metal rod interspace for their spectral positions, bandwidths, transmittances, and attenuation coefficients. Arranging metal rods with fine-tuning the interspaces across the optic axis is presented as the critical stratagem to optimize the transportation efficiency of THz waves through an MRA structure. The maximum propagation length of MRA-confined THz waves is over 30 mm with the lowest attenuation coefficients of approximately 0.05–0.1 cm−1. The MRA is, therefore, applicable as one deformable artificial structure in THz frequency region because simply one-axial adjustment of the metal-rod interspace enables the modulation purpose without uniform adjustment on the two-dimensional metal rod interspace.

Spectral Water Transparency of Novosibirsk Reservoir in Summer 2017

The results of measurement of the spectral attenuation coefficient of water at different depths and at wavelength 400–800 nm carried out at the Novosibirsk reservoir during August 14–18, 2017 are presented. The route of water sampling along the reservoir measured 200 km in length and consisted of ten sections from the town of Kamen-na-Obi to the dam area of hydropower station and the Berdsk Gulf. The hydrooptical measurements involved the evaluation of the depth of Secchi disk visibility. It is found that the largest spectral attenuation coefficient of water at wavelength 400–800 nm for the surface layer in the upper part of the reservoir reached 30 m-1. This is due to the high average flow rate reaching 1–15 m/s, shallow depth, turbulent mixing of water masses that leads to the increase of the concentration of suspensions and dissolved substances in water. In the middle part of the reservoir, where the average flow rate in the surface layer is reduced to 0.3–0.5 m/s, the highest spectral attenuation of water is observed at 8 m-1. At the bottom and dam parts of the reservoir, where the average flow rate is 0.11-0.20 m/s, the spectral attenuation of water does not exceed 6 m-1. The two sites of the Berdsk Gulf show the maximum spectral attenuation at 5.5–8 m-1. In general, the results of field investigations quantify the variations in the spectral attenuation of summer water at different depths for 10 sites of the three main parts of the Novosibirsk reservoir and the Berdsk Gulf. The obtained data provide a basis for the modeling of hydrophysical processes and the integrated assessment of the ecological state of the water body under study.DOI 10.14258/izvasu(2018)1-08

Parameter estimation in exponential models by linear and nonlinear fitting methods

Estimation of unknown parameters in exponential models by linear and nonlinear fitting methods is discussed. Based on the extreme value theorem and Taylor series expansion, it is proved theoretically that the parameters estimated by the linear fitting method alone cannot minimize the sum of the squared residual errors in the measurement data when measurement noise is involved in the data. Numerical simulation is performed to compare the performance of the linear and nonlinear fitting methods. Simulation results show that the linear method can obtain only a suboptimal estimate of the unknown parameters and that the nonlinear method gives more accurate results. Application of the fitting methods is demonstrated where the water spectral attenuation coefficient is estimated from underwater images and imaging distances, which supports the improvement in the accuracy of parameter estimation by the nonlinear fitting method.

Towards Cost-Effective Operational Monitoring Systems for Complex Waters: Analyzing Small-Scale Coastal Processes with Optical Transmissometry

The detection and prediction of changes in coastal ecosystems require a better understanding of the complex physical, chemical and biological interactions, which involves that observations should be performed continuously. For this reason, there is an increasing demand for small, simple and cost-effective in situ sensors to analyze complex coastal waters at a broad range of scales. In this context, this study seeks to explore the potential of beam attenuation spectra, c(λ), measured in situ with an advanced-technology optical transmissometer, for assessing temporal and spatial patterns in the complex estuarine waters of Alfacs Bay (NW Mediterranean) as a test site. In particular, the information contained in the spectral beam attenuation coefficient was assessed and linked with different biogeochemical variables. The attenuation at λ = 710 nm was used as a proxy for particle concentration, TSM, whereas a novel parameter was adopted as an optical indicator for chlorophyll a (Chl-a) concentration, based on the local maximum of c(λ) observed at the long-wavelength side of the red band Chl-a absorption peak. In addition, since coloured dissolved organic matter (CDOM) has an important influence on the beam attenuation spectral shape and complementary measurements of particle size distribution were available, the beam attenuation spectral slope was used to analyze the CDOM content. Results were successfully compared with optical and biogeochemical variables from laboratory analysis of collocated water samples, and statistically significant correlations were found between the attenuation proxies and the biogeochemical variables TSM, Chl-a and CDOM. This outcome depicted the potential of high-frequency beam attenuation measurements as a simple, continuous and cost-effective approach for rapid detection of changes and patterns in biogeochemical properties in complex coastal environments.

参与性介质中脉冲激光回波信号的角度特性

To improve the echo signal-to-noise ratio and temporal-spatial resolution of active detection systems further, the two-way transient radiative transfer model of ultrashort pulse laser in participating medium is established using Monte Carlo method. Based on the model above, the influence of medium properties and target reflective characteristic on the angular characteristic of Gaussian pulse laser echo signal in isotropic scattering medium is analyzed. Research shows that the incident zenith angles of target echo signal have reached its steady state in optically thick medium, with the peak angle interval of 30~40 and the energy concentration range of 30~50, but the temporal broadening characteristic is irrelevant to angle intervals; the spectral attenuation coefficient affects the energy attenuation and pulse width of echo signal strongly, but the scattering albedo embodies in the energy attenuation of post-echo signal mainly; high intensity pre-echo signal caused by specular reflection weakens, and the absolute difference of target echo signal is extremely small between specular reflection and diffuse reflection, with weaker relevance. The reference for gated-camera design selection and pulsed laser wavelength is provided. , 2015, Science Press. All right reserved.

Within-day variability of particulate organic carbon and remote-sensing reflectance during a bloom of Phaeocystis antarctica in the Ross Sea, Antarctica

We examined the within-day variability in seawater optical properties and biogeochemical constituents for a high-latitude location in the Ross Sea, Antarctica, during development of the annual spring phytoplankton bloom. Measurements of particulate organic carbon concentration (POC), chlorophyll-a concentration (Chl), and particle size distribution were conducted at 4–6 hour intervals in parallel with determinations of the spectral absorption and attenuation coefficients of particles, and the spectral remote-sensing reflectance of the surface ocean (Rrs). Surface POC and Chl exhibited more than a twofold variation throughout the day in the continuous presence of natural light. A minimum occurred near local noon coinciding with peak solar irradiance, a maximum in the evening, and a subsequent decrease throughout the night-time hours. These patterns were accompanied by large changes in the magnitude and spectral shape of Rrs, including the blue-to-green spectral band ratios used in ocean colour algorithms for estimating POC and Chl. The variability in Rrs could not be explained by changes in solar zenith angle, but was consistent with observations of within-day variations in spectral absorption and scattering by particles which were influenced by changes in the particle concentration and size distribution. The accuracy of an empirical ocean colour algorithm for estimating POC from Rrs was unaffected by within-day variability, implying that short-term variations in surface POC can be potentially monitored by multiple within-day measurements of Rrs, through means of in situ and remote sensing observations if available. Our findings also suggest that within-day changes in POC can be significant compared with the variability observed on meso-scale spatial scales, potentially confounding the interpretation of remote-sensing data obtained from temporal and spatial compositing of images measured at different times within a single day.

Object Detection by Estimation of the Spectral Attenuation Coefficient in the Submerged Medium

Underwater object detection has a considerable impact in the field of ocean technology. This paper presents a techniqueto detect a submerged object based on the medium's spectral attenuation coefficient by applying Beer-Lambert Law. The value of this coefficient is a function of the medium's composition, depth of the object,and wavelength of incident light. Experiments were performed in a swimming pool using objects of different colors at different depths to validate the mathematical model for object detection.

The characteristics of particulate absorption, scattering and attenuation coefficients in the surface ocean; Contribution of the Tara Oceans expedition

A dataset consisting of AC-S measurements of (hyper-) spectral particulate absorption, scattering and attenuation coefficients were obtained from measurements performed on the flow-through system of the R/V Tara during its 2.5-year long expedition.The AC-S instruments were robust, working continuously with weekly maintenance for about 3 months at a time, and provided absorption (attenuation) data for 454 (375) days, or 90% (75%) of total possible days during the expedition.This dataset has been mapped to 1 km×1 km bins to avoid over emphasizing redundant data, and to match the spatial scale of typical ocean color satellite sensors. It consists of nearly 70,000 particulate absorption spectra and about 60,000 particulate scattering and attenuation spectra. These data are found to be consistent with chlorophyll extraction and with the published average shapes of particulate absorption and scattering spectra and bio-optical relationships. This dataset is richer than previous ones in the data from open-ocean (oligotrophic) environments making it more representative of global distributions and of utility for global algorithm development.

Dynamics of phytoplankton distribution and photosynthetic capacity in a western Norwegian fjord during coastal upwelling: Effects on optical properties

The present study describes the coupling between optical properties and the dynamics of phytoplankton distribution and photosynthetic capacity in the Lysefjord during an exceptional coastal upwelling. At the mouth of the fjord, transparent Coastal water was “piled up” against the sill, while more turbid Fjord water from the outer fjord system was flowing over the sill, creating the intermediate layer which extended further into the fjord. This was reflected by high spectral attenuation coefficients in the upper 10 m of the fjord. Outside the sill, clear water with low spectral attenuation coefficients were found below sill depth down to at least 30 m, while the attenuation coefficients inside the sill were significantly higher between 10 and 20 m. About 4–7 km outwards from the head of the fjord clearer deep basin water was entering the upper layer due to the upwelling which could be traced up to 7 m, bounded by the 7.5 °C and the 31 salinity isolines. In the outer part of the fjord waters with a high chl a content and photosynthetic capacity were observed below the outflowing surface layer containing “old water” from the inner part of the fjord, which was characterized by low nutrient and chl a concentrations. Maximum quantum efficiencies (0.5) were encountered within this subsurface layer. Quantum efficiencies exceeded 0.3 when nitrate and silicate concentrations increased above 2 mmol m −3 . About 50% of the PAR light attenuation (0–30 m) was caused by chl a , and the 1% light depth varied between 27 and 35 m along the transect. Due to the influence of freshwater outlets, non-pigmented particles were more abundant in the inner part of the fjord than in the outer part. Colored dissolved organic matter (CDOM) contributed strongly to absorption within the upper 10 m at wavelengths below 470 nm while scattering was the major attenuation contributor for wavelengths above 600 nm. With respect to possible climate change effects on the growth of phytoplankton in Norwegian fjords, our results indicate that the alteration of coastal wind patterns due to its impact on coastal – fjord water exchanges, is probably more important than increased temperature and/or increased precipitation.

Variations in the optical properties of a particle suspension associated with viral infection of marine bacteria

A laboratory experiment was conducted to examine the temporal dynamics of the particle size distribution (PSD) and associated optical variability caused by viral infection of marine heterotrophic bacteria. The PSD covering a broad range of particle size from ≈ 50 nm to 200 µm was measured in parallel with the spectral particulate absorption and beam attenuation coefficients, from which the particulate scattering coefficient, bp(λ), was determined. Within 12 h following infection, the host bacterial population collapsed, viral abundance increased, and submicron particles were produced as bacteria were disrupted and cell debris released, resulting in a large decrease in bp(λ) seen as an almost complete clearing of the particle suspension. Throughout the remainder of the experiment, significant changes in the PSD occurred primarily within the size range of relatively large particles (> 4 µm), likely as a result of the aggregation of smaller‐sized particles originating from the host lysis. The PSD data were used as input for Mie scattering calculations to evaluate the effects of these particle dynamics in terms of relative contributions of different particle size classes to the scattering and backscattering coefficients. This analysis showed a significant increase in the effect of particle aggregation on light scattering during the second and third days after infection. Viral lysis of bacteria and subsequent particle dynamics produce large variations in the PSD over a broad size range on timescales from hours to a few days, and such processes lead to correspondingly large changes in the suspension optical properties.

Hyperspectral portable beam transmissometer for the ultraviolet‐visible spectrum

The spectral beam attenuation coefficient is an important optical property of natural water used to quantify light propagation and visibility in the aquatic media, and to study the concentration of the water constituents. Although beam attenuation in the ultraviolet spectral range may be particularly informative, to date, no transmissometer capable of measuring the beam attenuation in the ultraviolet is commercially available. The portable hyperspectral beam transmissometer developed in our lab is capable of measuring across a broad spectral range (300–750 nm) at 2 nm spectral resolution. The transmissometer exhibits a small acceptance angle (0.55 to 0.59° across the spectrum), a well collimated spectral light beam, and precision of ±0.012 m−1. The attenuation of diverse water samples measured with our transmissometer was found to be significantly similar to that measured with a commercially available transmissometer. Moreover, the attenuation of filtered samples, measured with our transmissometer, was significantly similar to their absorption, measured with a bench‐top spectrometer. Testing the transmissometer in the field, the transmission of water samples collected in Lake Malawi, Africa, was measured on site. The magnitude and spectral shape of attenuation were in general agreement with previous reports. All assessment stages confirm the performance, accuracy, and applicability of our transmissometer. The extended spectral range and high spectral resolution of our portable transmissometer make it an excellent tool for studying the characteristics and distribution of dissolved and particulate matter in aquatic media and exploring the constraints imposed on the visibility and visual communication of aquatic organisms known to have ultraviolet photosensitivity.

Spectral Irradiance and Phytoplankton Community Composition in a Blackwater-Dominated Estuary, Winyah Bay, South Carolina, USA

We investigated spatial and temporal relationships between spectral irradiance and phytoplankton community composition in the blackwater-influenced estuary Winyah Bay, South Carolina. Upstream, high concentrations of chromophoric dissolved organic matter (CDOM) absorbed blue wavelengths, resulting in a predominantly red light field. Green light prevailed downstream near the lower-CDOM coastal ocean, and phytoplankton community composition was distinct from upstream and mid-estuarine communities. Diatoms were abundant throughout the estuary in January, August, and October, cryptophytes dominated in July, and chlorophytes were abundant in December 2006. Only diatoms and chlorophytes showed significant covariation with the spectral attenuation coefficient (k(λ)): Chlorophytes showed positive relationships with k(442) (blue light) while diatoms were negatively correlated with k(442) and k(490) (violet to blue). Phytoplankton community composition in Winyah Bay appears to be driven by strong horizontal flow rather than gradients in spectral irradiance, but results indicate that water color is likely to play a greater role in blackwater-influenced estuaries with longer residence times.

Quantitative image‐based spectral reconstruction for computed tomography

Computed tomography (CT) devices are routinely employed to obtain three-dimensional images of the human body. The reconstructed CT numbers represent weighted x-ray attenuation coefficients. Their spectral weighting is influenced by the selected x-ray source spectrum, the detector characteristics, and the attenuating object itself. The quantitative ground truth of the scanned object is given by the spectral attenuation coefficient. It is not directly measurable in standard CT. For spectral CT measurements, algorithms like the basis material decomposition yield parametrized representations of the spectral mass attenuation coefficient. In practical applications, image-based formulations are commonly used. They are affected by both the CT system characteristics and the object self-attenuation effects. In this article the authors introduce an image-based spectral CT method. It expresses measured CT data as a spectral integration of the spectral attenuation coefficient multiplied by a local weighting function (LWF). The LWF represents the local energy weighting in the image domain, taking into account the system and reconstruction properties and the object self-attenuation. A generalized image-based formulation of spectral CT algorithms is obtained, with no need for additional corrections of, e.g., beam hardening. The iterative procedure called local spectral reconstruction yields both the mass attenuation coefficients of the object and a representation of the LWF. The quantitative accuracy and precision of the method are investigated in several applications: First, beam hardening corrections to various target energy weightings and attenuation correction maps for SPECT/CT and PET/CT are calculated. Second, an iodine density evaluation is performed. Finally, a direct identification of spectral attenuation functions using the LWF result is demonstrated. In all applications, the ground truth of the objects is reproduced with a quantitative accuracy in the subpercent to 2% range. An exponential convergence behavior of the iterative procedure is observed, with one to two iteration steps as a good compromise between quantitative accuracy and precision. The authors conclude that the method can be used to perform image-based spectral CT reconstructions with quantitative accuracy. Existing algorithms benefit from the intrinsic treatment of beam hardening and system properties. Novel algorithms are enabled to directly compare material model functions to spectral measurement data.

Using bio-optics to investigate the extent of coastal waters: A Swedish case study

In order to develop an optical model to map the extent of coastal waters, the authors analyzed variations in bio-optical constituents and submarine optical properties along a transect from the nutrient-enriched coastal bay, Himmerfjarden, out into the open Baltic Sea. The model is a simple implementation of the “ecosystem approach,” because the optical constituents are proxies for important components of ecosystem state. Yellow substance or colored dissolved organic matter (CDOM) is often a marker for terrestrial freshwater or decay processes in the littoral zone. Phytoplankton pigments, especially chlorophyll a, are used as a proxy for phytoplankton biomass that may be stimulated by fluvial or coastal inputs of anthropogenic nutrients. Suspended particulate matter (SPM) is placed in suspension by tidal or wind-wave stirring of shallow seabeds, and is therefore an indicator for physical forcing. It is the thesis of this article that such constituents, and the optical properties that they control, can be used to provide an ecological definition of the extent of the coastal zone. The spatial distribution of the observations was analyzed using a steady-state model that assumes diffusional transport of bio-optical variables along an axis perpendicular to the coast. According to the model, the resulting distribution along this axis can be described as a low-order polynomial (of order 1–3) when moving from a “source” associated with land to the open-sea “sink.” Order 1 implies conservative mixing, and the higher orders imply significant biological or chemical processes within the gradient. The analysis of the transect data confirmed that the trend of each optical component could be described well using a low-order polynomial. Multiple regression analysis was then used to weigh the contribution of each optical component to the spectral attenuation coefficient K d(490) along the transect. The results showed that in this Swedish Baltic case study, the inorganic fraction of the SPM may be used to distinguish between coastal and open-sea waters, as it showed a clear break between coastal and open-sea waters. Alternative models may be needed for coastal waters in which fronts interrupt the continuity of mixing.

G0601-4-2 断熱材の赤外線拡散透過特性と減衰係数の評価(熱工学(4)輻射・物性)

G0601-4-2 断熱材の赤外線拡散透過特性と減衰係数の評価(熱工学(4)輻射・物性)