Surface Measurements Research Articles

Prediction of Late Proximal Endoleak Risk after EVAR by Preoperative Estimation of Endograft/Aortic Neck Apposition Surface

The aim of this study was to evaluate a new measurement tool for the preoperative computed tomography (CT) scan to estimate the endograft apposition surface on the proximal aortic neck of the aneurysm that would predict the risk of late type IA endoleak (EL1A). From databases of 4 high-volume centers between 2004 and 2020, all patients who underwent Endovascular Aneuruysm Repair (EVAR) with the possibility of analyzing pre and post-EVAR scans and who presented late (>2years) EL1A in follow-up were included retrospectively (EL1A group). A control group of randomly selected EL1A-free patients were included (control group) and followed-up beyond 4years. The measurement tool (Endosize, Therenva) was used to model a virtual cylinder constrained by the centreline whose diameter was determined from the diameter of the implanted endograft. The apposition surface was calculated by determining the areas of the virtual cylinder mesh outside the mesh of the neighboring portion of the segmented aorta by an intersection calculation of surface normals. This apposition surface and the usual anatomical data of the proximal neck were compared between the groups with univariate and multivariate analyses. Intra and interobserver variability in the measurement of apposition surface was analyzed using the intraclass correlation coefficient (ICC) and the method of Bland and Altman. Sixty-six comparable patients were included as follows: 33 in the EL1A group and 33 in the control group. The mean time to EL1A onset was 50.2±24.6months in the EL1A group, and the mean follow-up time was 79.8±26.8months in the control group. In univariate analysis, only the endograft apposition surface ratio on the proximal neck was significantly lower in the EL1A group compared with the control group (50.3% vs. 75.5%; P < 0.0001). There was no significant difference in classic anatomical neck characteristics. There was no difference in proximal endograft oversizing or in the length from the lowest renal artery to the beginning of the covered portion of the endograft. In multivariate analysis, only the apposition surface ratio was independently correlated with the presence of EL1A (P < 0.0001). The estimation of the intra and interobserver variability indicates excellent reliability (ICC=0.992; ICC=0.956). The method estimating the preoperative endograft apposition surface on the proximal aortic neck appears to be a reliable measuring technique in predicting the risk of occurrence of late EL1A after EVAR.

Full-field three-dimensional system calibration for composite surfaces reconstruction

The accurate calibration of composite surface measurement systems for specular and diffused surface is of great importance in a number of industrial applications. This paper addresses the challenges in calibrating composite surface reconstruction by proposing a comprehensive full-field calibration method. The principal innovation is the construction of a comprehensive reference phase and the pixel-by-pixel calibration of system parameters within the same coordinate system. The details are as follows: (1) construct a complete reference phase for the composite surfaces through external parameter constraints phase fusion and interpolation; (2) calibrate the mapping relationship coefficients, compensate the accuracy degradation of the partial reflection. Experimental results validate the accuracy of the full-field calibration data, demonstrating the effectiveness and feasibility.

Physics-Informed Deep-Learning Models Improve Forecast Scalability, Reliability

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper URTeC 4042557, “Physics-Informed Deep-Learning Models for Improving Shale and Tight Forecast Scalability and Reliability,” by Kainan Wang, SPE, Lichi Deng, and Yuzhe Cai, SPE, Chevron, et al. The paper has not been peer reviewed. _ In the complete paper, the authors present a workflow that combines probabilistic modeling and deep-learning models trained on an ensemble of physics models to improve scalability and reliability for shale and tight reservoir forecasting. Their approach is applied to synthetic cases and many wells in the Permian Basin. Through hindsight studies, these models have been demonstrated to generate realistic and diverse production curves, capture the physics of unconventional flow, quantify well-production-outlook uncertainty, and help interpretation of subsurface uncertainty. Introduction In the realm of unconventional asset development, scalable forecasting is a key component in forecast reliability. In recent years, data-driven machine-learning models and workflows have emerged as potent tools for predicting well performance, particularly in scenarios where wells share similar reservoir properties, completion designs, and operational conditions. A novel approach known as physics-informed machine learning (PIML) has gained prominence. These models leverage the strengths of machine learning while honoring the constraints imposed by physical laws. By incorporating observational, inductive, or learning bias, they bridge the gap between empirical data and fundamental physics. In this paper, the authors showcase the application of a PIML system tailored specifically for unconventional reservoirs. Their methodology involves the selection of an appropriate physics modeling framework, coupled with the development of multiple machine-learning models that augment the limited field data set. Data Acquisition and Generation Bottomhole pressure (BHP) data are key to reliable forecasting because they reflect constraints to well production. Downhole pressure gauges can provide measurements of BHP accurately, but these measurements are not always available. Numerical models can be used to correlate surface measurements to BHP with some accuracy, taking into consideration the well configuration and fluid properties, yet it is too time-consuming to develop such models for many wells in relation to the speed needed for unconventional reservoir development. An in-house machine-learning model was developed for BHP calculation to further augment the data set of gauge measurements and numerical modeling. Through a workflow that chooses the wells with higher-fidelity data as a training set, and careful calibration and iterations between incrementally adding wells of high-fidelity data to reduce uncertainty, the trained machine- learning model is able to predict BHP accurately for many more wells. Another type of engineering data important for reliable well-performance analysis and forecasting is reservoir-fluid description. In this study, the authors leveraged an internally developed pressure/volume/temperature (PVT) machine-learning model trained on proprietary PVT data, which was also shown to provide reliable predictions to key PVT properties such as saturation pressure, formation volume factor, and viscosity from limited inputs at the reservoir and separator level. These PVT models not only enhance scalability of any downstream forecasting models but also play a crucial role in physics-informed uncertainty analysis for these models.

The capability of Acoustic Emission features to monitor diamond-coated burr grinding wear and effectiveness

Within manufacturing there is a growing need for autonomous Tool Condition Monitoring (TCM) systems, with the ability to predict tool wear and failure. This need is increased, when using specialised tools such as Diamond-Coated Burrs (DCBs) for grinding high strength ceramics or glass, in which the random nature of the tool, inconsistent manufacturing methods and high wear rates create large variance in tool life. This unpredictable nature leads to a significant fraction of a DCB tool's life being underutilised due to premature replacement. Workpiece surface damage, increased grinding forces and large-scale diamond grain pullout could all be the result of high levels of runout and in-circularity common within electroplated DCBs. As such it is important to not only monitor the overall tool wear but also tool condition. Acoustic Emission (AE) presents as an indirect on-machine sensing method highly suited to grinding applications. The high frequency range of AE, &gt;20 kHz, prevents machine noise from dominating the acquired signals, isolating the micro-scale machining processes within noises machine environments. AE resulting from the grinding process has the potential to monitor not only tool wear but also runout and circularity. A series of DCB wear tests have been conducted, each consisting of the continuous acquisition of AE during grinding and frequent tool surface measurements. Preliminary results demonstrate AE kurtosis can be seen as an indicator of each tool’s runout, representing the fraction of time the tool and workpiece are in contact during a revolution. As a result, an indirect monitoring system capable of monitoring wear and tool state with AE could be utilised within the manufacturing sector.

Comparison of Indoor Climate between Wooden wall Construction and Concrete Wall Construction during Winter Season

Abstract This research aims to determine the importance of thermal comfort in buildings, especially residential houses, with a focus on two types of houses that have different structures as a comparison. The research also focuses on productive rooms that are frequently used every day, considering the long duration of use. Data collection methods include distributing questionnaires to residents, as well as a quantitative approach using experiments and thermal measurements of temperature and humidity in each room, including surface measurements to compare the two types of buildings. The analysis results show that there are differences in thermal comfort between the two types of houses. Houses with wooden construction show relative humidity that reaches a comfortable point (45-65%), while houses with concrete construction tend to move cold temperatures from outside to indoors more quickly. Although efforts have been made to achieve thermal comfort in every room, the main challenge remains related to the energy consumption of artificial comfort systems. The study location in Japan took into account the different outdoor temperature variations each season. The findings we got were that houses with wooden construction walls tend to be warmer due to several factors, one of which is that this building is an apartment type with openings that tend to be smaller compared to buildings with wooden construction walls which are a traditional Japanese house type with wide openings. The measurement results using PMV analysis for both buildings were measured at 2 times at the same time, namely during the day and at night. Measurements were carried out in the living room as a comparison room with the function of a room that has the same user interaction between the two buildings. Honjo Nishi Danci Apartment (concrete wall construction) has a comfort level in the quite comfortable category compared to the living room in the apartment. Kitakyushu Islamic Cultural Center (wooden wall construction). Data was taken when both buildings did not turn on the air conditioner so that the data taken could be comparable. At night, the conditions in the living room have a slightly warm sensation because the user uses air conditioning in the room because the user sleeps in this room. the conditions in the living room at the Islamic Cultural Center have a cold sensation due to the lack of activity and use of this room. So the sensation at night tends to be cold. These findings can guide building designers in developing architectural solutions that are sustainable and focused on indoor comfort in winter.

Lava Worlds Surface Measurements at High Temperatures

First measurements of the emission of lava worlds with the James Webb Space Telescope (JWST) probe the conditions on worlds so hot that their surfaces are likely molten or partially molten. These observations provide a unique opportunity to explore rocky planets’ evolution. Surfaces of lava world exoplanets can give insights into their composition and their interior workings. However, data of spectral emissivity of a wide range of potential exoplanet surface compositions and temperatures is required to understand JWST data. Here, we chose eight synthetic, potential exoplanet surfaces that span a wide range of chemical compositions to provide observers with a tool for the interpretation of JWST data for the exploration of lava worlds. We present the measured infrared emissivity spectra (2.5–20 μm) of these materials for temperatures between 800° C and 1350° C. Our data comprise the first spectral library of possible high-temperature exoplanet surfaces. From these measurements, we establish the link between composition and a strong spectral feature at around 9 μm, the Christiansen frequency (CF) for different temperatures. Additionally, we report that the shift in the CF associated with the bulk composition of the material is significantly more important than its temperature. This provides a critical tool to aid in interpreting future spectra of lava worlds that will be collected by the JWST and future missions.

Optical 3D Surface Vertical Measurement Based on 2D Generalized S-Transform

Abstract The optical 3D surface measurement technique aligns the optical axis of the projector with that of the camera, enabling the measurement of objects with significant height variations, such as deep holes and grooves. This technique encodes the height of the object into the modulation of the fringe pattern, eliminating the requirement for phase unwrapping and avoiding issues such as shadow occlusion. To further enhance the noise reduction capability of fringe analysis and reconstruct objects with high-frequency detail, this paper introduces the two-dimensional generalized S-transform (2D-GST) method for modulation extraction. By incorporating two additional parameters px and py to adjust the resolution in the time domain/frequency domain, 2D-GST can provide higher reconstruction precision. The root mean square (RMS) for tested plane with 2D-GST is 4.35 μm, whereas for the traditional 1D S-transform (1D-ST), the RMS is 4.97 μm.

Low-cost electronic speckle pattern interferometry: Obtaining reliable signals

Designs for low cost electronic speckle pattern interferometry (ESPI) systems allow broad use of this technique to study the vibration or deformation of surfaces. For example, the technique allows direct imaging of the normal mode shapes of musical instruments, which can be used to assess design changes or optimize instrument fabrication. While the typical surface measurement system is quite simple in design, obtaining reliable signals is often challenging. Random phase changes due to object motion or reference signal light path can lead to decorrelations resulting in an unstable final image that washes out with averaging. Depolarization of the scattered light also diminishes the interference pattern intensity. We will be discussing the particulars of surface preparation, optical alignment, and phase control that help lead to successful ESPI image contrast and stability. We will also discuss the differences between using a stationary reference image for ESPI subtraction and a frame-by-frame difference method to obtain higher contrast interference patterns.

Evolution of Single Photon Lidar: From Satellite Laser Ranging to Airborne Experiments to ICESat-2

In September 2018, NASA launched the ICESat-2 satellite into a 500 km high Earth orbit. It carried a truly unique lidar system, i.e., the Advanced Topographic Laser Altimeter System or ATLAS. The ATLAS lidar is capable of detecting single photons reflected from a wide variety of terrain (land, ice, tree leaves, and underlying terrain) and even performing bathymetric measurements due to its green wavelength. The system uses a single 5-watt, Q-switched laser producing a 10 kHz train of sub-nanosecond pulses, each containing 500 microjoules of energy. The beam is then split into three “strong” and three “weak” beamlets, with the “strong” beamlets containing four times the power of the “weak” beamlets in order to satisfy a wide range of Earth science goals. Thus, ATLAS is capable of making up to 60,000 surface measurements per second compared to the 40 measurements per second made by its predecessor multiphoton instrument, the Geoscience Laser Altimeter System (GLAS) on ICESat-1, which was terminated after several years of operation in 2009. Low deadtime timing electronics are combined with highly effective noise filtering algorithms to extract the spatially correlated surface photons from the solar and/or electronic background noise. The present paper describes how the ATLAS system evolved from a series of unique and seemingly unconnected personal experiences of the author in the fields of satellite laser ranging, optical antennas and space communications, Q-switched laser theory, and airborne single photon lidars.

Panoramic evaluation of external root resorption in mandibular molars during orthodontic treatment: a comparison between root-filled and vital teeth treated with fixed appliances or clear aligners

BackgroundThis investigation compared the extent of external apical root resorption (EARR) in root-filled teeth (RFT) and their contralateral vital pulp teeth (VPT) counterparts during orthodontic treatment (OT) with clear aligner (CA) treatment or fixed appliance (FA) treatment.MethodsSixty-six patients with similar baseline American Board of Orthodontics (ABO) discrepancy index scores were divided into two groups: 37 patients (21 females, 16 males; mean age 17.45 ± 2.67 years) in the FA group, and 29 patients (18 females, 11 males; mean age 18.33 ± 1.96 years) in the CA group. Digital panoramic radiographs captured pre- and post-OT were used to measure tooth lengths and root surface measurements in mandibular molars. EARR in both RFT and contralateral VPT was evaluated pre- and post-OT. Statistical analysis employed paired t-tests, independent t-tests, and analysis of covariance (ANCOVA) (p < .05).ResultsAll teeth exhibited varying degrees of EARR following OT. FA treatment resulted in significantly longer treatment duration (p < .05) and greater EARR compared to CA treatment (p < .05). Moreover, statistically significant differences in EARR were observed within both groups between RFT and VPT (p < .05).ConclusionsComparison of pre- and post-OT radiographs revealed different degrees of EARR in all teeth. CA treatment resulted in less frequent and less severe EARR compared to FA treatment. RFT demonstrated greater resistance to EARR than VPT in both treatment groups.

Calibration of the spherical tip radius of Rockwell hardness diamond indenters using a confocal laser scanning microscope

Abstract The precise form of an indenter is an essential part of hardness testing methods. It is therefore incumbent upon a user to ensure that the indenter geometry is calibrated before performing a hardness test. A geometric change of the tip radius by ±5 μm can cause a change of approximately 0.6 units of Rockwell hardness C scale (HRC) in a material with a hardness of 65 HRC. Keeping in mind that the measurement uncertainty is typically of the order of 0.3 HRC, it is critical to know the true value of the tip radius. Typically, tactile methods are used to determine the tip radius of a Rockwell hardness diamond indenter from the measured surface topography. Two main drawbacks of tactile measurements are the long duration of measurement and the limitation in capturing surface features of sizes smaller than the probe tip radius of 2 μm. Both could be overcome by using an optical 3D measurement. Confocal laser scanning microscopes (CLSM) allow a fast contactless 3D-mapping of the surface of Rockwell hardness diamond indenters and can be used to obtain geometric information such as the tip radius. The accuracy of these 3D measurements is still under question. Within this work, some of the influencing factors for fast 3D surface measurement are investigated. Using a CLSM with a 50x objective lens and a numerical aperture of 0.95, typical shape deviations of Rockwell diamond indenters are shown. Furthermore, an improved 3D based point cloud method for the evaluation of the indenter radius is presented. The aim of this paper is to explore the capabilities and limits of CLSM to obtain the 3D surface of a Rockwell hardness diamond indenter in order to calibrate the tip radius and compare their results with measurements from traceable stylus instruments.

Photogrammetry is a useful tool to assess the aesthetic outcome after excision and reconstruction of the nose skin tumors

BackgroundobjectivePost-oncological nasal reconstruction presents both aesthetic and functional challenges. While established methods exist for quantitatively evaluating functional results following surgery, equivalent systems for assessing aesthetic outcomes are lacking. Three-dimensional (3D) photogrammetry, already used in maxillofacial and orthodontic surgery for aesthetic evaluation, overcomes some limitations of traditional methods like direct anthropometry. However, its applicability in oncological facial reconstruction has not yet been explored. In our study, we applied the 3dMDtrio™ system for the quantitative analysis of line and surface modifications following nasal reconstruction. MethodsWe conducted a prospective observational study enrolling patients with skin neoplasms located on the nose undergoing surgical excision and reconstruction. Using the 3dMDtrio™ system, we measured the dimensions and projections of nasal surfaces and the positions of specific landmarks before and after surgery. The surface measurements were then correlated with aesthetic evaluations performed by three plastic surgeons, not involved in the procedure, using a 5-point Likert scale. ResultsWe included 33 patients with a mean age of 71 years, ranging from 40 to 94. We obtained complete documentation of all postoperative measurements for 21 patients. We observed significant changes in the positions of the landmarks post-surgery, limited to the right ala and nasion. The average nasal surface area was 4674.41 mm2 ± 477.24 mm2 before surgery and 4667.95 mm2 ± 474.12 mm2 after surgery, with no significant discrepancies. The evaluation using the Likert scale revealed an average score of 3.04 ± 0.48, with a significant negative correlation to the measured surface changes. ConclusionOur findings suggest that 3D photogrammetry can be considered a valid method for objectively assessing volumetric changes associated with post-oncological nasal reconstructive surgery.

Prior-shape-guided photometric stereo model for 3D damage measurement of worn surfaces

Three-dimensional (3D) damage measurement often encounters limited accuracy due to the non-Lambertian effects on worn surfaces. To address this issue, a prior-shape-guided surface reconstruction model is introduced with photometric stereo vision. Initially, an illumination calibration method is constructed to mitigate the uneven brightness on worn surface images. Subsequently, a prior-shape-guided network is developed that employs the feature aggregation strategy and prior shape uncertainty to guide worn surface reconstruction. Experimental results reveal that the proposed model can effectively recover the typical morphologies of worn surfaces, and the root mean square error is reduced from 7.39 to 1.59 when compared to existing methods. Most importantly, this model has been applied to detect aero-engine bearings and achieve 3D quantitative characterization for worn damages.

Development and Validation of an Affordable Calibration Method for Surface Plates

The measurement and calibration of flat surfaces is highly relevant for precision engineering, length metrology, and optical systems. Hence, many National Metrology Institutes (NMIs) tend to offer calibration services in this regard. Typically, mechanical, electromechanical, and optical measuring techniques are applied, with uncertainties in the order of micrometers. However, these techniques necessitate expensive equipment that requires periodical calibration and maintenance, which not many laboratories can afford. This work presents the validation of an affordable and simple calibration technique for surface plates through the evaluation of metrological compatibility with a reference calibration method. A surface plate was calibrated with both methods under the same conditions to validate our proposal. The 2.9 µm uncertainty obtained with the new method demonstrates its reliability and usability for laboratories with surface plates up to 300 mm in length that have a grade AA to B flatness accuracy. Due to its low initial cost, reliability, and ease of implementation, the proposed calibration method can be recommended to all laboratories and industries that need to constantly verify their surface plates.

Optical Target Projector: Principle of Functioning and Basic Performance Test.

Faced with measurement conditions such as high-temperature forging, strict prohibition of surface contamination, and toxic environments, using the projection point of an optical target projector (referred to as an "optical projector") as a photogrammetric target has become a necessary method of high-precision industrial photogrammetry. In connection with the current industrial demand, we have analyzed the principles of optical projectors and introduced their optical characteristics and advantages in the field of industrial photogrammetry. On this basis, a series of tests such as brightness, roundness, and so on were conducted to determine the basic properties of the optical projector. A set of performance test methods including inner coincidence accuracy and outer coincidence accuracy were proposed; the tests included industrial photogrammetry system measurement repeatability, surface measurement precision, and a comparison test with laser tracker. The test conditions used optical projection points as the photogrammetry targets. The test results showed that the coordinate measurement repeatability of the industrial photogrammetry system is 0.010 mm, and the surface measurement precision is 0.007 mm under the condition of a single optical projector station, with little difference between the results under the condition of pasting retro-reflective targets. In the process of the comparison test with laser tracker, the image quality of the black measurement object obtained is obviously inferior to other surfaces, so the analysis of the point projector is greatly affected by the color of the measured object and other conditions, which provides a reference for the measurement object and application range of the industrial photogrammetric system based on optical targets. The results demonstrate the applicability and reliability of using the optical projection point of an optical projector as target points for photogrammetry.

Evaluation of surface texturing on chrome-coated cylinder liners via deterministic mixed lubrication simulation

This study investigates the mixed lubrication performance of various surface texture configurations in the piston ring/cylinder liner conjunction of a two-stroke internal combustion engine using a deterministic mixed lubrication model. The numerical model simultaneously solves the Reynolds equation with mass-conserving cavitation to calculate inter-asperity hydrodynamic pressures and an elastic, perfectly plastic, rough contact model to determine contact pressures at each asperity interaction. Gaussian Mixture Model clustering was employed to enhance surface characterization. The deterministic simulation approach considers the full-scale representation of the cylinder liner topography to accurately capture the influence of surface features on the hydrodynamic support and friction under mixed lubrication conditions. The investigated cylinder liners were initially hard-chrome-coated and honed, resulting in a stochastic arrangement of surface pores, and then deterministic patterns of surface pockets were created by micro electrodischarge machining (EDM). Surface measurements were performed using laser interferometry, providing input for the mixed lubrication simulations. The study also explored the virtual removal of ridges formed around the pockets by the EDM technique. Key findings indicate that the stochastic texture outperformed the hybrid texture (stochastic + deterministic) in the boundary and mixed lubrication regimes, showing higher hydrodynamic support at low separations but increased hydrodynamic shear stresses at higher speeds. Conversely, deterministic textures exhibited a significant decrease in average hydrodynamic shear stress at high velocities. These results highlight the critical role of surface texture in tribological behavior and suggest that localized textures on cylinder liners can potentially optimize engine performance. The study recommends further exploration of a broader range of texture geometries, densities, and distribution patterns to enhance engine design strategies.

Dynamic deformation measurement with 2-frame phase-shifting speckle interferometry based on speckle statistics and wavefront multiplexing.

Phase-shifting speckle interferometry could achieve full-field deformation measurement of rough surfaces. To meet the dynamic requirement and further improve the accuracy, a two-step synchronous phase-shifting measurement system is established based on the polarization-sensitive phase modulation ability of a liquid crystal spatial light modulator; by multiplexing the reference wavefront, an accurate phase shift is generated between two independent recording channels, and a common-path self-reference vortex interference structure is built for precise spatial registration. Meanwhile, according to the speckle statistical principle, a novel two-frame phase-shifting algorithm as well as a two-step spatial registration strategy is presented to strengthen the robustness of intensity and position differences caused by spatial-multiplexing; thereby, accurate transient deformation can be directly obtained from phase-shifting speckle interferograms recorded before and after deformation. The effectiveness and accuracy of the proposal are validated from the out-of-plane deformation measurement experiment by comparing with the traditional two-step and four-step phase-shifting methods. The dynamic ability is exhibited through reconstructing mechanical and thermal deformations across various application scenarios.

Multimodal mechano-microscopy reveals mechanical phenotypes of breast cancer spheroids in three dimensions.

Cancer cell invasion relies on an equilibrium between cell deformability and the biophysical constraints imposed by the extracellular matrix (ECM). However, there is little consensus on the nature of the local biomechanical alterations in cancer cell dissemination in the context of three-dimensional (3D) tumor microenvironments (TMEs). While the shortcomings of two-dimensional (2D) models in replicating in situ cell behavior are well known, 3D TME models remain underutilized because contemporary mechanical quantification tools are limited to surface measurements. Here, we overcome this major challenge by quantifying local mechanics of cancer cell spheroids in 3D TMEs. We achieve this using multimodal mechano-microscopy, integrating optical coherence microscopy-based elasticity imaging with confocal fluorescence microscopy. We observe that non-metastatic cancer spheroids show no invasion while showing increased peripheral cell elasticity in both stiff and soft environments. Metastatic cancer spheroids, however, show ECM-mediated softening in a stiff microenvironment and, in a soft environment, initiate cell invasion with peripheral softening associated with early metastatic dissemination. This exemplar of live-cell 3D mechanotyping supports that invasion increases cell deformability in a 3D context, illustrating the power of multimodal mechano-microscopy for quantitative mechanobiology in situ.

Surface and average volume temperature measurements in semitransparent media based on multispectral thermotransmittance

Temperature plays an essential role in maintaining the performance of microsystems, which calls for three-dimensional mapping of heat sources, hot spots and thermal properties. In this context, infrared (IR) thermography provides information for opaque materials but faces limitations when applied to semitransparent samples such as microfluidic chips or semiconductor materials in the IR range. In this article, we present temperature maps obtained for the surface and average volume of two semitransparent samples with a detection limit of 1 K. To achieve such measurements, we demonstrated that thermotransmittance signals can be decomposed into two parts: the first originating from interfaces and the second originating from the volume. We quantified the contributions of both components by combining contactless measurements with a heat transfer model. We then validated the method using two Borofloat glass samples with different thicknesses. We were able to discriminate the contributions of surface and volume temperatures by performing spectroscopic thermotransmittance measurements at wavelengths ranging from 3100 to 3400 nm due to the different spectral behaviors of these two components. This new technique is an important improvement for temperature measurements using IR cameras in semitransparent media.

Evaporating temperature estimation of refrigeration systems based on vibration data-driven soft sensors

The evaluation of the operating conditions of refrigeration compressors once installed in household appliances is challenging due to the need to install pressure transducers, a process which requires system evacuation and refrigerant reintroduction. In addition, changes in the piping modify the characteristics of the original product. This paper proposes a soft-sensing technique based on vibration measurements of the compressor surface to predict the evaporating temperature. Different machine learning (ML) techniques are evaluated as data-driven prediction models, namely multilayer perceptron (MLP) neural networks, least squares boosting, generalized additive model, random forest, extreme learning machine, and random vector functional link neural networks. These techniques were applied to data obtained from a test rig designed to emulate compressor operation in a refrigeration system, with an operating envelope from -30°C to -10°C for the evaporating temperature and from 34°C to 54°C for the condensing temperature. The results showed that, with a single vibration measurement point, it was possible to use an MLP technique to estimate the evaporating temperature with a root mean squared error of 1.74°C in a non-intrusive way. For the other prediction techniques, the errors were a bit higher than for the MLP, but the maximum error value was about 2.5°C in all cases.