Soil moisture is a key parameter in several applications, from land management to emergency response. Microwave-based soil moisture products are already provided daily, yet at 1 km resolution. Optical remote sensing could be a complementary source of information at higher spatial resolution (10-100 m), but most studies have been limited to highly homogeneous scenarios. In this paper, the potential of optical images to assess soil moisture in a highly-fragmented scenario is investigated. Landsat-8 optical data were processed to retrieve the Visible and Shortwave Drought Index (VSDI) over an area with heterogeneous land cover. Results were compared with the Copernicus Soil Water Index (SWI) product, showing a moderate correlation (Pearson coefficient equal to 0.402) that however increases to 0.668 if only bare soil pixels are selected.

Bolt connections are a critical component in steel structure design. After a period of operation, bolts in steel structures may experience loosening due to prolonged external forces or fatigue, posing a potential threat to overall structural safety. Currently, the practical method for detecting loose bolts in steel structures typically involves contact-based assessment, specifically using a torque wrench for testing. However, given the numerous bolts in a connection design, this contact-based evaluation method is inefficient for large-scale bridge bolt connection areas and is extremely time-consuming. To address this issue, this preliminary study explores the use of infrared thermography to assess bolt temperature changes during connection behavior and further evaluate bolt tightness. The analysis method integrates advanced image processing and time series analysis techniques to identify abnormal temperature distribution and temperature gradients in the connection area, establishing quantifiable indicators for bolt temperature status.

Vibrothermography is an effective non-destructive testing technique for detecting closed defects like cracks and delaminations through frictional heat generated under ultrasonic excitation. However, its accuracy is often reduced by standing wave patterns that create periodic temperature artifacts in non-defective areas, leading to false positives. To overcome this, we propose an image processing approach using 2D Fourier Transform (2D-FFT) to reduce SW-induced patterns in the frequency domain. This enhances defect visibility by suppressing unwanted heat signatures. The method is evaluated on a cracked PMMA plate and a hollow tube of the same material.

This study evaluates the bonding condition of concrete slabs with varying porosity levels (20% to 80%) at cold joint interfaces by analyzing surface wave dispersion ve-locity profiles. A dual-receiver setup was employed to compare the waveform and dispersion characteristics along the test lines that crossed cold joints and those that did not. While wave velocity reduced for lower wavelengths at lower void levels, more significant reductions were observed across the entire wavelength range at higher porosity levels. This demonstrates that Rayleigh-wave dispersion can effectively assess cold joints generated by artificial voids with known void ratios.

This study addresses the detection of gunshot residue (GSR) around a bullet hole, which is one of the key forensic procedures for estimating firing distance. GSR was inspected using Flash-Pulse Thermography (FPT) with kurtosis statistical processing. The result of such an inspection is a pattern composed of numerous small indications distributed around the hole, attributed to gunshot residue particles. The number and spatial distribution of these indications depend on the firing distance. Analyzing such results based on individual indications is impractical, as the pattern must be evaluated as a whole. Therefore, quantifying the overall result can significantly improve the analysis of the firing distance estimation. This study presents a quantification procedure based on threshold-based mass-marking of indications and evaluation of several statistical characteristics. The correlation between these characteristics and firing distance is then analyzed. A strong but distinctly nonlinear correlation was found between the firing distance and some simple quantitative characteristics, such as the total number of indications. However, the study shows that some derived characteristics, such as the contrast between marked areas and background, exhibit a near-linear correlation. These parameters are, therefore, promising for firing distance analysis based on FPT inspection of GSR on through-shot targets.

An infrared thermographic technique was developed for identifying the thermal diffu-10sivity from temperature variation data of specimen surface. A laser-spot heating is applied to the11specimen surface for a certain period and then temperature variation of the surface is measured12using infrared thermography. Since analytical solution for the temperature variation is expressed13in terms of parameters including the thermal diffusivity,thickness and heating pointposition,the14parametersare identifiedby fitting theanalytical solution to the measured data. The developed15technique was applied to a ceramic specimen for verification. It was shown that the thermal diffu-16sivity can be identified with high accuracyif the thickness and heating pointpositionare known17in advance. Furthermore, it is confirmed thatthe thermal diffusivity, thickness, and heating point18positioncan be simultaneously estimated with acceptable accuracy.

In additive manufacturing (AM), particularly with AlSi10Mgaluminumalloy produced via Laser14Powder Bed Fusion (L-PBF), understanding and detecting defects is crucial for ensuring mechanical integrity.15This study evaluates the effectiveness of active thermography as a fast, non-destructive testing (NDT) method16for identifying typical L-PBF defects. Artificial defects (cubes, spheres, cylinderswith unfused powder) were17introduced by varying printing parameters. Their real geometry was assessed via micro-computed tomography18(μ-CT), revealing deviations from nominal shapes. Thermographic tests using a laser heat source (≈40W/cm²)19were conducted to examine the detectability of these defects inthishighly diffusive material AlSi10Mg. Results20highlight both the limitations and potential of thermography as a cost-and time-effective alternative toμ-CT21for quantitative inspection.

Many of Japan's infrastructures are more than 50 years old afterconstruction,11and their aging is expected to accelerate in the future.Therefore, the challenge is to in-12spect the deteriorated condition of those infrastructures.This study focuses on the use of13electromagnetic waves in NDT as an inspection method for infrastructure.One issue14with this method is that the device is not suitable for actual infrastructure inspections.15We constructed a portable reflection measurement system that utilizes sub-terahertz16waves among electromagnetic waves.Reflection measurementswere conducted on cor-17roded and uncorroded steel plates using this compact system.It may be possible to18identify samples using peak shift with a horn antenna. With a probe antenna, identifica-19tion is based on reflectance.

Infrared thermography, with its ability to obtain information remotely and non-contact, is often applied as a valuable method for investigating the surface layers of historical buildings. In this paper, the results of applying infrared thermography during academic investigations of two Italian treasures—the Sanctuary of Vicoforte in Piedmont and the airship hangar in Augusta, Sicily—are presented. At the Sanctuary of Vicoforte, imaging was performed to evaluate the condition of the exterior finishes and interior frescoes, while at the airship hangar, imaging was conducted to detect cracks that are difficult to observe using visible-light imaging.

Laser Powder Bed Fusion (L-PBF) of AlSi10Mg is challenged by rapid thermal transients and high diffusivity. This study applies a microbolometer-based thermal monitoring system to correlate laser power, scan speed, and build position with thermal features. Results demonstrate reliable detection of defects such as keyhole porosity, supporting real-time process control and quality assurance.