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The mostly subterranean nature of district heating system pipelines makes pinpointing any occurring leakages a challenge. Airborne thermography offers a means for widespread monitoring, allowing thermal anomalies to be identified within multitudes of infrared images. This paper details a program developed to automate the entire image analysis process using mainly open-source software. Thermal images are acquired via unmanned aircraft system (UAS), pre-processed, and georeferenced individually or combined to orthomosaics. The search space is minimized to areas around the pipelines. Regions of interest are determined by image segmentation via tailored triangle histogram thresholding. The majority of resulting false alarms are removed by comparison with characteristic traits and results classified by their severity. The algorithm is applied to images newly acquired in Germany as part of a case study. The implemented methodology allows for a reduction of between 92 and 99% of thermal anomalies to a manageable amount of potential leakages for network operators to view. The use of orthomosaiking software in this context, though helpful in coalescing data, is found to lack robustness, precision and therefore reliability. Despite some limitations, the developed program is able to confidently detect and categorize leakages of varying severity and can be used directly by network operators. Future research will focus on further data pre-processing to eliminate thermal drift and remove the remaining false alarms, which mostly pertain to common urban features. [ABSTRACT FROM AUTHOR]

Highlights • Heat treatment of bamboo slows down the rate of water absorption. The short term water absorption of bamboo reduces from 7.5% per hour and for not heated specimens to about 3% per hour when subjected to 200 °C for 24 h. The weight increment due to natural water observation for bamboos heated in different temperatures is around 100%. The untreated specimens can absorb more water up to 20% in comparison with treated bamboo at 225 °C for 3 h. Heating bamboo up to 225 °C for 3 h or 200 °C for 24 h reduces the water absorption capacity up to 15% compared with the non-heated specimens. The effect of heating at 175 °C for 24 h is the same as heating at 200 °C for 3 h and both can reduce significantly the swelling in radial and tangential directions due to water absorption. The long term water absorption of treated and unheated bamboo for four weeks follows a three phase model; rapid, transition and slows for all heated cases for 3 and 24 h. There is no significant difference between shrinkage at external and internal parts of a bamboo section. The swelling of external side of bamboo due to water absorption in average is about 40% more than the internal part. The fibers expand five times more than the matrix due to water absorption up to saturation point. The fiber swelling coefficient does not change up to 200 °C and a drop of 2% after this temperature. The matrix swelling coefficient is 4% at 100 °C and gradually decreases to 2% at 225 °C. Abstract The main objective is to present the results of an investigation on the effect of heat and time exposure on hygroscopic property of Dendrocalamus giganteus bamboo. The shrinkage and water absorption of bamboo segments in longitudinal, radial and tangential directions, due to heat effect of seven different temperatures from ambient to 225 °C during 3 h and 24 h has been investigated. An equation based on the principal of curve fitting has been established for rapid, transition and slow phases of water absorption. The non-uniform shrinkage and water absorption tests in tangential direction at different temperatures during 3 h carried out to obtain the fiber and matrix shrinkage and water absorption separately. The water absorption test result shows that by increasing the temperature and time exposure the hygroscopic property of bamboo is reduced. Subjecting to heat at higher temperatures can slow down the rate of water absorption in short term. [ABSTRACT FROM AUTHOR]

An experimental investigation on the forced convective subcooled flow boiling of water was carried out using image processing. Three copper test parts of different roughness were tested at different operational conditions established through a design of experiments, covering bulk velocities from 0.1 m/s to 0.9 m/s, bulk temperature from 76.5 °C to 93.5 °C, and operating pressures from 110 kPa to 190 kPa. The boiling process has been maintained on the nucleate regimen varying heat flux from 0.1 MW/m 2 to 1 MW/m 2 , though image processing was only feasible below 0.65 MW/m 2 . The result of the experimental work is a database of the size distribution of the bubbles at each experimental point and presented as an electronic annex. The results confirmed that bubbles are generally smaller at higher pressure, higher velocities and higher levels of subcooling. The effect of surface morphology proved to be a very strong factor that is normally ignored by correlations and experimental works. Finally, an analysis of the possibility of the interaction of surface morphology with bubble size is presented. [ABSTRACT FROM AUTHOR]

Infrared thermography coupled with a special image processing was employed to study the heating process of AZ31B magnesium alloy during the high-cycle fatigue process. Heat-conduction effect was subtracted from thermal data provided by an infrared camera to study the heat-dissipation rate evolutions. Three stages of temperature variation were observed before the initiation of macroscopic crack, when the stresses were above the fatigue limit and below the yield limit. Severe work-hardening effect led to a drastically degradation in plastic deformability, and also caused the heat-dissipation rate dropped steeply from the maximum to the saturation value. The correlation between temperature distribution and stress distribution was also investigated. At different stress level, the temperature distributions in a single sample are different. Finally, an improved graphical method was proposed to estimate with good approximation of the fatigue limit of AZ31B magnesium alloy more readily. The proposed method showed basically satisfied results comparing with the conventional method. [ABSTRACT FROM AUTHOR]

District heating is a common way of providing heat to buildings in urban areas. The heat is carried by hot water or steam and distributed in a network of pipes from a central power plant. It is of great interest to minimize energy losses due to bad pipe insulation or leakages in such district heating networks. As the pipes generally are placed underground, it may be difficult to establish the presence and location of losses and leakages. Toward this end, this work presents methods for large-scale monitoring and detection of leakages by means of remote sensing using thermal cameras, so-called airborne thermography. The methods rely on the fact that underground losses in district heating systems lead to increased surface temperatures. The main contribution of this work is methods for automatic analysis of aerial thermal images to localize leaking district heating pipes. Results and experiences from large-scale leakage detection in several cities in Sweden and Norway are presented. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Effects of long-duration heating on pulse phase thermography were investigated. [•] Larger amounts of heat can be input easily using long-duration heating. [•] The greater heat input engenders lower amplitude of noise in phase images. [•] For detection of deep defects, long-duration heating enhances the phase contrast. [•] Detectable defect depth was improved by application of long-duration heating. [Copyright &y& Elsevier]

Highlights: [•] We reconstruct heat sources from temperature fields using a derivative Gaussian filter. [•] Synthetic temperature fields corrupted by noise enabled us to optimise the filter. [•] The influence of both the dimension and the level of a localised heat source is discussed. [•] Experimental fields on aluminium plates heated by electric patches were processed. [•] The relevancy of the filter to reliably reconstruct heat source fields is demonstrated. [ABSTRACT FROM AUTHOR]

ITER first wall (FW) includes a beryllium armour joined to a Cu heat sink with a stainless steel back plate. These FW panels are one of the critical components in the ITER tokamak with a maximum surface heat flux of 5 MW/m2. Therefore, a qualification test needs to be performed with the goal to qualify the joining technologies required for the ITER FW. Various mock-ups were fabricated to develop the manufacturing procedure of FW components. For the nondestructive examination of the fabricated mock-ups, an ultrasonic test (UT) was performed with optimized probes. The UT was performed by using a three-axis digital ultrasonic C-scan system and software. The system comprised an ultrasonic pulser and receiver, model Panametrics 5800PR; a personal computer having an internal analog/digital converter board and four-axis motion control board; and a three-axis scanning tank. Two types of transducers were used for this experiment. One was Panametrics V312-SU, having a center frequency of 10 MHz (nominal) and a piezoelectric element diameter of 0.25 in with a flat protective layer for the Be/Cu. The other was Panametrics V309-SU with a center frequency of 5 MHz and an element diameter of 0.5 in for the Cu/SS interface. Winspect software controlled all aspects of data acquisition, motion control, data archiving, and image display. Based on the acceptance criteria, the average amplitude of the interface signals, which have about 50% of the reference echo amplitude, was recorded and analyzed on each beryllium tile. An image-analysis software analyzed the statistics of amplitude distribution and calculated the unacceptable area. Each mock-up that passed these UTs was concluded to qualify the joining technologies required for an ITER FW by using a high-heat flux test facility. As a result of these qualification tests based on the acceptance criteria of an ITER FW, the fabrication technologies will be utilized to develop the FW of plasma-facing components. [ABSTRACT FROM PUBLISHER]

Electronic circuit boards of computers consist of components which generate substantial amounts of heat during their operation. Among these, the microprocessor chip is one of the major sources of heat generation. In high-performance processor chips, the rates of heat generation are also correspondingly high. The performance of the chips themselves, as well as that of the neighboring electronic components are affected by the temperature levels attained, which in turn depend on the heat dissipation capability. Effective thermal management of microprocessor chips, following precise thermal characterization, is essential to avoid their untimely failure due to overheating. The selection of an appropriate cooling methodology and the design of an efficient cooling system for the microprocessor chip essentially require a clear knowledge of the heat dissipation rates during its operation. A comprehensive database of heat dissipation from microprocessor chips as a function of the activity level, based on actual measurements, is rare to find in the literature. A major reason for this is that conventional intrusive measurements on and around the chip are quite insufficient, as they will alter the performance, while the system is under operation. To overcome this, a nonintrusive digital interferometric measurement has been devised in this paper for obtaining the in situ temperature distributions and the heat dissipation patterns around the microprocessor chip, while it is under operation. The interferometric method utilizes interference of coherent laser beams to make measurements in the thermal field around the heat-dissipating component. An Intel Pentium 4 microprocessor with its integrated heat sink was used for experimentation. The computational load on the processor was varied utilizing a software package, thus varying the heat generation rates, and the base temperature of the fins in the heat sink attached to the microprocessor. Interferometric measurements were made to obtain the temperature distribution in the medium, and the patterns of heat dissipation from the fins' surfaces. Indicators of the heat transfer behavior, namely, the local heat flux values and the heat transfer coefficients were obtained from the experiments, using digital image processing techniques. Experiments were conducted at various fin-base temperatures, under free and forced convection conditions, to characterize the effect through a database of the heat dissipation level. In essence, a nonintrusive temperature measurement method coupled with digital image processing techniques has been successfully used for convective heat transfer studies on the microchip while the microchip is under operation. [ABSTRACT FROM PUBLISHER]

We propose a method to compute scale-invariant features in omnidirectional images. We present a formulation based on the Riemannian geometry for the definition of differential operators on non-Euclidian manifolds that adapt to the mirror and lens structures in omnidirectional imaging. These operators lead to a scale-space analysis that preserves the geometry of the visual information in omnidirectional images. We then build a novel scale-invariant feature detection framework for omnidirectional images that can be mapped on the sphere. We further present a new descriptor and feature matching solution for these omnidirectional images. The descriptor builds on the log-polar planar descriptors and adapts the descriptor computation to the specific geometry and the nonuniform sampling density of omnidirectional images. We also propose a rotation-invariant matching method that eliminates the orientation computation during the feature detection phase and thus decreases the computational complexity. Experimental results demonstrate that the new feature computation method combined with the adapted descriptors offers promising detection and matching performance, i.e., it improves on the common scale-invariant feature transform (SIFT) features computed on the unwrapped omnidirectional images, as well as spherical SIFT features. Finally, we show that the proposed framework also permits to match features between images with different native geometry. [ABSTRACT FROM PUBLISHER]

In this paper, we present a framework for detecting interest points in 3-D meshes and computing their corresponding descriptors. For that, we propose an intrinsic scale detection scheme per interest point and utilize it to derive two scale-invariant local features for mesh models. First, we present the scale-invariant spin image local descriptor that is a scale-invariant formulation of the spin image descriptor. Second, we adapt the scale-invariant feature transform feature to mesh data by representing the vicinity of each interest point as a depth map and estimating its dominant angle using the principal component analysis to achieve rotation invariance. The proposed features were experimentally shown to be robust to scale changes and partial mesh matching, and they were compared favorably with other local mesh features on the SHREC'10 and SHREC'11 testbeds. We applied the proposed local features to mesh retrieval using the bag-of-features approach and achieved state-of-the-art retrieval accuracy. Last, we applied the proposed local features to register models to scanned depth scenes and achieved high registration accuracy. [ABSTRACT FROM PUBLISHER]

Lock-in (LI) thermography is a popular thermal-nondestructive-testing technique which, like other active thermographic techniques, requires an external heating stimulus, preferably on a blackened surface. It is not, however, immune to nonideal situations like nonuniform heating and surface emissivity variation. The phase image, to some extent, helps to reduce the effect of these artifacts but is inadequate if the variations are large. For example, a poorly blackened metallic sample with reflecting patches on its surface is very difficult to actively thermograph because of direct reflection from the surface. This paper proposes an image reconstruction algorithm for offline removal of such artifacts. In addition, the proposed algorithm enables LI thermography tests in the transient regime and removes temperature gradients due to nonuniform heating. The algorithm was tested with a mild-steel sample having 20-mm-diameter back-drilled holes at various depths ranging from 0.2 to 7.7 mm, stimulated at 20-, 40-, 50-, 60-, and 80-mHz excitation frequencies. The effect of the total number of heating cycles is also presented. [ABSTRACT FROM PUBLISHER]

This paper introduces a class of adaptive Perona–Malik (PM) diffusion, which combines the PM equation with the heat equation. The PM equation provides a potential algorithm for image segmentation, noise removal, edge detection, and image enhancement. However, the defect of traditional PM model is tending to cause the staircase effect and create new features in the processed image. Utilizing the edge indicator as a variable exponent, we can adaptively control the diffusion mode, which alternates between PM diffusion and Gaussian smoothing in accordance with the image feature. Computer experiments indicate that the present algorithm is very efficient for edge detection and noise removal. [ABSTRACT FROM AUTHOR]

A new method for the nondestructive measurement of moisture content (MC) distribution in timber during drying was developed using X-ray computed tomography (CT) scanning and image processing techniques. The deformed cross section in the CT images due to shrinkage was corrected with the image registration, and the shrinkage was measured by digital image correlation analysis. The pixel-wise MC distributions during drying were measured and visualized successfully. The total timber MC estimated from the MC values of each pixel were strongly correlated with those measured by calculation without geometrical transformation of CT images. The coefficient of determination (R 2) and the standard error of prediction (SEP) were 0.99 and 0.18%, respectively, within the MC range of 19.2–47.3%. In addition, the measured shrinkage distribution during drying was in accordance with the diamonding deformation observed. The results suggest that CT scanning combined with image processing techniques is an effective tool for nondestructive assessment of MC distribution during drying. [ABSTRACT FROM AUTHOR]

The optical scheme and design of a four-frequency polarizing microscope intended for simultaneous recording of plasma images in the wavelength range 0.4-1.1 μm with the spatial resolution 12 μm in the entire spectral range are described. The effectiveness of such a microscope in studies of plasmas produced on interaction of laser radiation with a target is demonstrated. The plasma images are obtained at the frequencies ω, (3/2)ω, 2ω, and (5/2)ω, where ω corresponds to the frequency of heating radiation. The transformation coefficient that characterizes the efficiency of conversion of heating radiation into the 2ω, (3/2)ω, and (5/2)ω harmonics generated in the plasma is determined. [ABSTRACT FROM AUTHOR]

Abstract: Proposed manuscript describes the implementation of a two step processing procedure, composed of the self-referencing and the Principle Component Thermography (PCT). The combined approach enables the processing of thermograms from transient (flash), steady (halogen) and selective (induction) thermal perturbations. Firstly, the research discusses the three basic processing schemes typically applied for thermography; namely mathematical transformation based processing, curve-fitting processing, and direct contrast based calculations. Proposed algorithm utilizes the self-referencing scheme to create a sub-sequence that contains the maximum contrast information and also compute the anomalies’ depth values. While, the Principle Component Thermography operates on the sub-sequence frames by re-arranging its data content (pixel values) spatially and temporally then it highlights the data variance. The PCT is mainly used as a mathematical mean to enhance the defects’ contrast thus enabling its shape and size retrieval. The results show that the proposed combined scheme is effective in processing multiple size defects in sandwich steel structure in real-time (<30Hz) and with full spatial coverage, without the need for a priori defect-free area. [Copyright &y& Elsevier]

Abstract: Due to the complicated processes for coal particles burning in industrial furnaces, their radiative properties, such as the absorption and scattering coefficients, which are essential to make reliable calculation of radiative transfer in combustion computation, are hard to be given exactly by the existing methods. In this paper, multiple color image detectors were used to capture approximately red, green, and blue monochromatic radiative intensity images in the visible wavelength region, and the flame emissivity and the radiative properties of the particulate media in three pulverized-coal-fired boiler furnaces were got from the flame images. It was shown that as the load increased, the flame emissivity and the radiative properties increased too; these radiative parameters had the largest values near the burner zone, and decreased along the combustion process. Compared with the combustion medium with a low-volatile anthracite coal burning in a 670 t/h boiler, the emissivity and the absorption coefficient of the medium with a high-volatile bituminous coal burning in a 1025 t/h boiler were smaller near the outlet zone, but were larger near the burner zone of the furnace, due to the significant contribution of soot to the radiation. This work will be of practical importance in modeling and calculating the radiative heat transfer in combustion processes, and improving the technology for in situ, multi-dimensional visualization of large-scale combustion processes in coal-fired furnaces of power plants. [Copyright &y& Elsevier]

In this paper, an empirical mode decomposition (EMD) method is applied to image processing in pulsed infrared thermographic testing. Through analysis of the Mode Function of an image EMD, characterisations of noise and uneven heating are given. Using the EMD method, noise and uneven heating are reduced at the same time and the contrast of the thermal image is improved. Finally, the result of pulsed infrared thermographic testing is given. Compared with other methods such as neighbourhood averaging, homomorphic filtering and background subtraction, this method is simple and effective to overcome noise and uneven heating in thermography. [ABSTRACT FROM AUTHOR]

The transition phenomenon of branched positive streamer to single filamentary discharge (SFD) with increase of the discharge-frequency was studied using a fast intensified charge coupled-device camera and an image converter camera. In addition, the gas temperature in SFD was measured by spectroscopic measurement. As a result, it was found that the transition to SFD progresses with localized gas heating along discharge channel. Furthermore, it was revealed that SFD is a nonbranched positive streamer. [ABSTRACT FROM PUBLISHER]

Thermal considerations can no longer be ignored The ongoing pursuit of faster, more-reliable and less-expensive electronic products is making thermal performance an increasingly 'hot' topic. Efficient board layout techniques can […]