Level Of Compression Research Articles

Using a micro-device with a deformable ceiling to probe stiffness heterogeneities within 3D cell aggregates

Recent advances in the field of mechanobiology have led to the development of methods to characterise single-cell or monolayer mechanical properties and link them to their functional behaviour. However, there remains a strong need to establish this link for three-dimensional (3D) multicellular aggregates, which better mimic tissue function. Here we present a platform to actuate and observe many such aggregates within one deformable micro-device. The platform consists of a single polydimethylsiloxane piece cast on a 3D-printed mould and bonded to a glass slide or coverslip. It consists of a chamber containing cell spheroids, which is adjacent to air cavities that are fluidically independent. Controlling the air pressure in these air cavities leads to a vertical displacement of the chamber’s ceiling. The device can be used in static or dynamic modes over time scales of seconds to hours, with displacement amplitudes from a few µm to several tens of microns. Further, we show how the compression protocols can be used to obtain measurements of stiffness heterogeneities within individual co-culture spheroids, by comparing image correlations of spheroids at different levels of compression with finite element simulations. The labelling of the cells and their cytoskeleton is combined with image correlation methods to relate the structure of the co-culture spheroid with its mechanical properties at different locations. The device is compatible with various microscopy techniques, including confocal microscopy, which can be used to observe the displacements and rearrangements of single cells and neighbourhoods within the aggregate. The complete experimental and imaging platform can now be used to provide multi-scale measurements that link single-cell behaviour with the global mechanical response of the aggregates.

ANALYSIS OF THE RESULTS OF PERCUTANEOUS VERTEBROPLASTY OF COMPRESSION FRACTURES OF BODIES OF CHEST AND LUMBAR VERTEBRAE ON THE BACKGROUND OF OSTEOPOROSIS

It is well known that the most frequent complication of osteoporosis is compression fractures of vertebral bodies. In addition to brittleness of the bones and mechanical stress, more and more evidence approving that compression fractures of vertebral bodies are related to many risk factors, such as aging, sex, concomitant morbidities of cardiovascular and cerebrovascular diseases and lifestyle (chronic smoking and alcohol consumption) are collected. Objective. Analyzing the condition of spines of the patients suffering from compression fractures of vertebral bodies on the background of osteoporosis after the performed Percutaneous vertebroplasty (PV). Methods. 553 patients who underwent hospital treatment at the spine pathology clinic of the Sytenko Institute of Spine and Joint Pathology (2005–2022) and underwent PV were examined. Results. The patients were divided into three groups depending on the number of damaged vertebrae. The 1st group included the patients with compression fractures of one vertebra (185 — 33.4 %); the 2nd group included the patients having 2 or 3 deformed vertebrae (216 — 39 %); and the 3rd group included the patients with 4–5 damaged vertebrae (152 — 27.4 %). Stages of compression of vertebral bodies during the X-ray morphometry was as follows before the surgery: I — 349 (24 %) vertebrae; II — 494 (34 %); III — 552 (38 %); and IV — 58 (4 %). We achieved the reduction of the level of compression of vertebral bodies as a result of PV in 20 % of cases (patients who noticed the manifestation of the pain syndrome within 2 weeks mostly suffered from these deformations). Conclusions. The results of analysis of PV of 553 patients with composite material and bone cement in the near and far future provide us an opportunity to state that this surgical treatment is an efficient and safe treatment method (despite the materials used). 40 (24 %) patients out of 165 patients of the group I, 52 (33 %) patients out of 157 patients of the group II and 54 (44 %) patients our of 133 patients of the group III were diagnosed with repeated compression fractures. Summarizing all the above, we should note that the more compression fractures the patient has, the higher the risk of further augmentation of other deformations of vertebral bodies is.

A Novel “De-tension”-guided Anterior Decompression Strategy—Thoracic Anterior Controllable Antedisplacement Fusion (TACAF) for Multilevel Ossification of Posterior Longitudinal Ligament in Thoracic Spine: A Retrospective Study with at Least 2-Year Follow-Up

To propose a novel surgical strategy-thoracic anterior controllable antedisplacement fusion (TACAF) to treat multilevel thoracic ossification of the posterior longitudinal ligament (mT-OPLL), and investigate its safety and efficacy. Between January 2019 and December 2021, a total of 49 patients with thoracic myelopathy due to mT-OPLL surgically treated with TACAF were retrospectively reviewed. Patients' demographic data, radiologic parameters, and surgery-related complications, modified Japanese Orthopedic Association (mJOA) and visual analog scale (VAS) scores, thoracic kyphosis (TK), kyphosis angle in fusion area (FSK), thoracic curvature, spinal cord curvature, and curvature of curved rod in surgical region, diameter, and area of the spinal cord at the most compressed level were included. All patients acquired satisfactory recovery of neurologic function and overall complication rate was low at the final follow up. The mean mJOA of the laminectomy+TACAF and Full Lamina Preservation+TACAF groups, respectively, was 3.74 ± 2.05, 3.67 ± 1.95 before surgery, and 9.97 ± 0.83, 9.80 ± 0.68 at the final followed up, with the recovery rate of 84.26% ± 14.20%, 82.79% ± 10.35%, as to VAS Scores. The mean FSK was 34.50 ± 4.46,35.33 ± 3.44 before surgery, and was restored to 20.97 ± 5.70, 22.93 ± 6.34 at the final followed up respectively, as to mean TK (P < 0.05). Spinal cord curvature was improved from 34.12 ± 3.59, 33.93 ± 3.45 before surgery to 19.47 ± 3.53, 18.80 ± 3.17 at the final follow-up respectively, as to thoracic curvature (P < 0.05). In addition, the area and diameter of the spinal cord was also significantly improved at the final follow up (all P < 0.05). The curvature of the thoracic pulp and thoracic vertebra is closely related to the curvature of the rod. There was no statistically significant difference in the incidence of the pelvis and the slope value of the sacrum. This strategy provides a novel solution for the treatment of mT-OPLL with favorable recovery of neurological function, the tension of spinal cord, and fewer complications.

Damage Detection in Bridge Structures through Compressed Sensing of Crowdsourced Smartphone Data

Traditional bridge health monitoring methods that necessitate sensor installation are not only costly but also time-consuming. In contrast, utilizing smartphone data collected from vehicles as they traverse bridges offers an efficient and cost-effective alternative. This paper introduces a cutting-edge damage detection framework for indirect monitoring of bridge structures, leveraging a substantial volume of acceleration data collected from smartphones in vehicles passing over the bridge. Our innovative approach addresses the challenge of collecting and transmitting high-frequency data while preserving smartphone battery life and data plans through the integration of compressed sensing (CS) into the crowdsensing-based monitoring framework. CS employs random sampling and signal recovery from a significantly reduced number of samples compared to the requirements of the Nyquist–Shannon sampling theorem. In the proposed framework, acceleration signals from vehicles are initially acquired using smartphone sensors, undergo compression, and are then transmitted for signal reconstruction. Subsequently, feature extraction and dimensionality reduction are performed using Mel-frequency cepstral coefficients and principal component analysis. Damage indexes are computed based on the dissimilarity between probability distribution functions utilizing the Wasserstein distance metric. The efficacy of the proposed methodology in bridge monitoring has been substantiated through the utilization of numerical models and a lab-scale bridge. Furthermore, the feasibility of implementing the framework in a real-world application has been investigated, leveraging the smartphone data from 102 vehicle trips on the Golden Gate Bridge. The results demonstrate that damage detection using the reconstructed signals obtained through compressed sensing achieves comparable performance to that obtained with the original data sampled at the Nyquist measurement sampling rate. However, it is observed that to retain severity information within the signals for accurate damage severity identification, the compression level should be limited to 20%. These findings affirm that compressed sensing significantly reduces the data collection requirements for crowdsensing-based monitoring applications, without compromising the accuracy of damage detection while preserving essential damage-sensitive information within the dataset.

Magneto-acousto-electrical tomography using nonlinearly frequency-modulated ultrasound.

Objective. In this study, nonlinearly frequency-modulated (NLFM) ultrasound was applied to magneto-acousto-electrical tomography (MAET) to increase the dynamic range of detection.Approach. Generation of NLFM signals using window function method-based on the principle of stationary phase-and piecewise linear frequency modulation method-based on the genetic algorithm-was discussed. The MAET experiment systems using spike, linearly frequency-modulated (LFM), or NLFM pulse stimulation were constructed, and three groups of MAET experiments on saline agar phantom samples were carried out to verify the performance-respectively the sensitivity, the dynamic range, and the longitudinal resolution of detection-of MAET using NLFM ultrasound in comparison to that using LFM ultrasound. Based on the above experiments, a pork sample was imaged by ultrasound imaging method, spike MAET method, LFM MAET method, and NLFM MAET method, to compare the imaging accuracy.Main results. The experiment results showed that, through sacrificing very little main-lobe width of pulse compression or equivalently the longitudinal resolution, the MAET using NLFM ultrasound achieved higher signal-to-interference ratio (and therefore higher detection sensitivity), lower side-lobe levels of pulse compression (and therefore larger dynamic range of detection), and large anti-interference capability, compared to the MAET using LFM ultrasound.Significance. The applicability of the MAET using NLFM ultrasound was proved in circumferences where sensitivity and dynamic range of detection were mostly important and slightly lower longitudinal resolution of detection was acceptable. The study furthered the scheme of using coded ultrasound excitation toward the clinical application of MAET.

Effective Permittivity of Compacted Granular Materials: Effects of Interfacial Polarization and Pore-filling Fluids

Interfacial polarization dominates the permittivity spectra of heterogeneous granular materials for the intermediate frequency range (i.e., from kHz to MHz). In this study, we examine the corresponding dielectric responses of compacted glass sphere packings saturated with pore-filling fluids under various compressive stresses. The effective permittivity spectra are observed to exhibit consistently a plateau-to-plateau drop, described by low-frequency permittivity, characteristic frequency, and high-frequency permittivity. The permittivity spectra under different compressive levels are found to be influenced by the packing structure, compressive stress, and electrical property contrasts between solid and fluid (specifically permittivity and conductivity). For considered measurement conditions, the variation of packing structure and its associated porosity is found to be more significant than the stress evolution in controlling the interfacial polarization, thus the permittivity spectra, as supported by analytical and numerical results for unit cells. Furthermore, to gain a general rule for dielectric responses for saturated granular materials, we train multi-layer artificial neural network (ANN) models based on a series of simulations for unit cells with various structures, stresses, and electrical and dielectric properties. The predictions with two-layer ANN agree well with experimental measurements, presenting errors smaller than 5% for both low-frequency and high-frequency permittivity. This study offers an effective predicting approach for the dielectric behaviour of heterogeneous and multiphase materials.

Enhancing fatigue performance of AZ31 magnesium alloy components fabricated by cold metal transfer-based wire arc directed energy deposition through LPB

Cold Metal Transfer-Based Wire Arc Directed Energy Deposition (CMT-WA-DED) presents a promising avenue for the rapid fabrication of components crucial to automotive, shipbuilding, and aerospace industries. However, the susceptibility to fatigue of CMT-WA-DED-produced AZ31 Mg alloy components has impeded their widespread adoption for critical load-bearing applications. In this study, a comprehensive investigation into the fatigue behaviour of WA-DED-fabricated AZ31 Mg alloy has been carried out and compared to commercially available wrought AZ31 alloy. Our findings indicate that the as-deposited parts exhibit a lower fatigue life than wrought Mg alloy, primarily due to poor surface finish, tensile residual stress, porosity, and coarse grain microstructure inherent in the WA-DED process. Low Plasticity Burnishing (LPB) treatment is applied to mitigate these issues, which induce significant plastic deformation on the surface. This treatment resulted in a remarkable improvement of fatigue life by 42%, accompanied by a reduction in surface roughness, grain refinement and enhancement of compressive residual stress levels. Furthermore, during cyclic deformation, WA-DED specimens exhibited higher plasticity and dislocation density compared to both wrought and WA-DED + LPB specimens. A higher fraction of Low Angle Grain Boundaries (LAGBs) in WA-DED specimens contributed to multiple crack initiation sites and convoluted crack paths, ultimately leading to premature failure. In contrast, wrought and WA-DED + LPB specimens displayed a higher percentage of High Angle Grain Boundaries (HAGBs), which hindered dislocation movement and resulted in fewer crack initiation sites and less complex crack paths, thereby extending fatigue life. These findings underscore the effectiveness of LPB as a post-processing technique to enhance the fatigue performance of WA-DED-fabricated AZ31 Mg alloy components. Our study highlights the importance of LPB surface treatment on AZ31 Mg components produced by CMT-WA-DED to remove surface defects, enabling their widespread use in load-bearing applications.

190 Do Fractional Anisotropy and Apparent Diffusion Coefficient From Diffusion Tensor Imaging Correlate to Symptoms of Radiculopathy? A Case Series From BACPAC MRI

INTRODUCTION: Quantitative diffusion tensor imaging (DTI) parameters such as fractional anisotropy (FA) and apparent diffusion coefficient (ADC) are used to detect axonal pathology in nerve injuries. METHODS: Ganglia of the lumbar plexus nerves (L1-5) were input as seeds to track the nerve fibers using Constant Solid Angle reconstruction. Fiber tracts and values of FA and ADC were extracted along the lumbar plexus nerve profiles. Change in pain (VAS) and disability (ODI) after interlaminar epidural steroid injection at site of compression was compared to the changes in FA and ADC values. RESULTS: Five exams from three patients with bilateral L4-5 foraminal narrowing were included in this study. Two patients were imaged at two time points, three months apart. The average age of the cohort was 62.6 ± 5.3 years. Mean FA values were lowest at L3 (left: 0.32 ± 0.08; right: 0.35 ± 0.05) and L4 (left: 0.39 ± 0.06; right: 0.38 ± 0.03). Correspondingly, mean ADC values were highest at L3 (left: 0.0017 ± 0.0002; right: 0.0016 ± 0.0001) and L4 (left: 0.0.0013 ± 0.0001; right: 0.0015 ± 0.0002). For one patient, pain did not change in severity and ODI improved from severe to moderate disability after steroid injection: FA increased with no significant change in ADC. For another patient, pain increased from moderate to severe and ODI stayed the same after injection: FA decreased and ADC did not significantly change. CONCLUSIONS: The tractography generated from the segmentation model demonstrated lowest FA and highest ADC values corresponding to the level of compression. For patient outcomes, the FA values were observed to be more sensitive to changes in pain and disability compared to the ADC values.

245 Linking Cervical Spinal Cord White Matter Magnetization Transfer Ratio to NIH Toolbox Based Analyses of Motor Function in Degenerative Cervical Myelopathy

INTRODUCTION: Traditional spine imaging technique present disparity between degenerative cervical myelopathy (DCM) disease severity and prognosis. Advancement in spine neuroimaging has unveiled key changes that enhance our understanding of DCM pathogenesis. We investigated region- and tract-specific SC white matter (WM) damage and their relationship to motor deficit in DCM. METHODS: A cohort of 20 DCM and 23 age-matched HC participants were recruited in a cross-sectional study. We utilized a consensus MT-imaging protocol, Spinal cord Toolbox, and objective motor assessment tool battery to assess the extent of WM injury and functional deficits in DCM. The SC WM region- and tract-based MTR were calculated in three different ROIs: maximum compressed level (MCL), caudal uncompressed level (C7), and central region of compression. RESULTS: DCM patients demonstrated significant functional deficits compared to HC in motor assessments. DCM exhibited reduced MTR measures denoting WM injury in the anterior region of the SC and within selected motor tracts in the ROIs. MTR values in reticulospinal, vestibulospinal, and lateral corticospinal tracts were significantly associated with dexterity and grip strength measures. CONCLUSIONS: Our methodology enables precise mapping of ROIs within the SC allowing us to demonstrate an association between tract-specific WM damage and functional motor deficits in DCM patients. Additionally, the observation of decreased MTR measures in seemingly uncompressed SC regions indicates the pathophysiology of DCM that may provide insight into the varying presentations of DCM. Identification of specific WM injury may help better understand DCM deficits that can be targeted for effective interventions to improve patient outcomes

Abstract 3384: Rapid and automated tumor cell phenotyping based on annexin-mediated enforce blebbing response

Abstract Introduction: Accumulating evidence supports the tight correlation between the physical characteristics of cells (including morphology, mechanical, and electrical properties) with the progression of cancer. Cellular blebbing, a distinctive feature observed during apoptosis and cell migration, has gained significant recognition. However, existing tools such as atomic force microscopy and optical tweezers have limitations in terms of throughput and complexity. Microfluidics has emerged as a promising technology to overcome these limitations. Methods: In this study, we developed a novel microfluidic device with a double-layer compression mechanism to induce controlled blebbing of cells. We implemented a convolution-based tracing program to enhance the accuracy and efficiency of cell area measurement. The device was used to examine the enforced blebbing response of two human breast cancer cell lines (MDA-MB-231 and MCF-7) and investigate the potential of blebbing as a marker for drug resistance using a human lung cancer cell line (HCC4006). Additionally, we elucidated the role of annexin-6 (A6) in enforced blebbing and its underlying mechanism. Results: Our microfluidic device successfully implemented a double-layered design that induced cell deformation through compression from the second pressurized polydimethylsiloxane layer. The findings revealed that highly invasive cell lines, such as MDA-MB-231 and osimertinib-resistant HCC4006, required significantly higher critical compression levels compared to their non-invasive counterparts (MCF-7 cell line) or osimertinib-sensitive cells. Moreover, the drug-resistant groups exhibited a greater compression strain requirement for blebbing compared to the control group, indicating their enhanced resilience against disruptive forces and superior survivability. Prior studies have demonstrated that A6 protein is recruited to the site of membrane injury and facilitates the formation of blebs, thereby contributing to cellular repair processes. Our further investigation into the role of A6 protein demonstrated its involvement in cell blebbing. Knockdown of A6 resulted in a notable 27% reduction in cellular volume, reflecting reduced intracellular pressure, and a corresponding 1.7-fold increase in the critical compressive strain necessary for inducing blebbing. Conclusion: Our microfluidic device allows for rapid and simultaneous testing and automated analysis of hundreds of cells, making it suitable for applications such as cell sorting, highly invasive and drug-resistant cancer cell detection, without the need for labeling. Furthermore, it serves as a powerful tool for fundamental studies of membrane and cytoskeleton dynamics. The label-free nature of the device, coupled with its high throughput capabilities, highlights its potential in future applications, including cancer monitoring and drug-resistance screening. Citation Format: Wei Huang, Zheng Wang, Dennis Wai-Yin Au, Bingxian Tang, Baiqian Qi, William C. Cho, Yuan Lin. Rapid and automated tumor cell phenotyping based on annexin-mediated enforce blebbing response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3384.

Evaluation of computed tomography artefacts of carbon-fiber and titanium implants in patients with spinal oligometastatic disease undergoing stereotactic ablative radiotherapy

This study evaluated artefacts on computed tomography (CT) images using Hounsfield units (HU) in patients with spinal oligometastatic disease who received carbon-fiber (CF; n = 11) or titanium (n = 11) spine implants and underwent stereotactic ablative radiotherapy (SABR). Pre- and postoperative HU were measured at the vertebral body, pedicle, and spinal cord at three different levels: the lower instrumented vertebra, the level of metastatic spinal cord compression, and an uninvolved level. Areas measured at each level were delicately matched pre- and postoperatively. Significant differences in HU were observed at the vertebral body, the pedicle, and the spinal cord at the lowest instrumented vertebra level for both CF and titanium (average increase 1.54-fold and 5.11-fold respectively). At the metastatic spinal cord compression level, a trend towards a higher HU-increase was observed in titanium compared with CF treated patients (average increase 2.51-fold and 1.43-fold respectively). The relatively high postoperative HU-increase after insertion of titanium implants indicated CT artefacts, while the relatively low HU-increase of CF implants was not associated with artefacts. Less CT artefacts could facilitate an easier contouring phase in radiotherapy planning. In addition, we propose a CT artefact grading system based on postoperative HU-increase. This system could serve as a valuable tool in future research to assess if less CT artefacts lead to time savings during radiotherapy treatment planning and, potentially, to better tumoricidal effects and less adverse effects if particle therapy would be administered.

Development of a Cissus quadrangularis-Doped Extracellular Matrix and a Hyaluronic Acid-Incorporated Scaffold for Periodontal Regeneration: An In Vitro Study.

The study aimed to analyze whether adding Cissus quadrangularis (CQ) extract and the extracellular matrix of ovine tendon (TENDON) increases the regenerative potential of mesenchymal stem cells produced in hyaluronic acid (HA) scaffolds for tenogenesis. Fifty grams of powdered CQ was mixed with 250 mL of ethanol to prepare the extract. Two grams of hyaluronic acid powder was added to 100 mL of distilled water to make the HA solution. The ovine tendon was decellularized using a mixture of 10% phosphate-buffered saline (PBS), sodium dodecyl sulfate (SDS), and Triton-X. The hydrogel samples were prepared by mixing the extracellular matrix of tendon, HA, and CQ, after which they were divided into study groups such as HA, HA + CQ, HA + TENDON, and HA + CQ + TENDON. Scanning electron microscopy (SEM) analysis, swelling analysis, differentiation analysis, compression test, compatibility assay, and tenogenesis assay were later conducted. The morphology of the samples was analyzed using SEM. Low levels of swelling of the hydrogels were observed. Cells were found to be viable and showed good differentiation and tenogenesis. Optimal compression levels were observed, and the properties of the prepared hydrogels were satisfactory. The results suggest that the addition of CQ considerably increases the tenogenic potential of the extracellular matrix/HA scaffold. Hence, it can be used as a regenerative material for periodontal tissue regeneration.

On compression level of hypersonic airflow in high-mach scramjet

High-Mach scramjet is one of the most promising air-breathing propulsion devices to realize integration of air and space transportation. The current paper investigates a key step in design of high-Mach scramjet, namely, the compression level to be executed. The influence of compression level on hydrogen-fuel scramjet performance was analyzed using the modified thermodynamic cycle analysis method for high-Mach conditions. The theoretical results indicate that different from classical thermodynamic cycle analysis, the scramjet thrust reaches the maximum when Mach number at the entrance of combustor approaches 3. The flow loss and heat release in scramjet reach a balance near the maximum thrust state. Excessive compression can cause severe flow loss, while insufficient compression will lead to poor combustion. The numerical simulation further supports the theoretical analysis. When compression level of airflow is inadequate, the heat release rate of fuel will significantly drop. To extended the ideal operating range of high-Mach scramjet, it is suggested that the flow loss in inlet and isolator should be minimized, and the combustion efficiency of fuel in supersonic environment should be improved.

Deep Convolutional Neural Network Compression Method: Tensor Ring Decomposition with Variational Bayesian Approach

Due to deep neural networks (DNNs) a large number of parameters, DNNs increase the demand for computing and storage during training, reasoning and deployment, especially when DNNs stack deeper and wider. Tensor decomposition can not only compress DNN models but also reduce parameters and storage requirements while maintaining high accuracy and performance. About tensor ring (TR) decomposition of tensor decomposition, there are two problems: (1) The practice of setting the TR rank to be equal in TR decomposition results in an unreasonable rank configuration. (2) The training time of selecting rank through iterative processes is time-consuming. To address the two problems, a TR network compression method by Variational Bayesian (TR-VB) is proposed based on the Global Analytic Solution of Empirical Variational Bayesian Matrix Factorization (GAS of EVBMF). The method consists of three steps: (1) rank selection, (2) TR decomposition, and (3) fine-tuning to recover accumulated loss of accuracy. Experimental results show that, for a given network, TR-VB gives the best results in terms of Top-1 accuracy, parameters, and training time under different compression levels. Furthermore, TR-VB validated on CIFAR-10/100 public benchmarks achieves state-of-the-art performance.

Chloride penetration resistance of concrete under dual effects of leaching and stress

Chloride penetration is one of the main causes for the failure of reinforced concrete structures, especially in undersea tunnels, which is also accompanied by stress and seepage water-induced calcium leaching. In this paper, the chloride penetration resistances of concrete under the single and dual effects of stress and calcium leaching were investigated, and the microscopic mechanism was explained by Scanning Electron Microscopy (SEM) and X-ray diffraction analysis (XRD). The results show that the chloride diffusion depth and chloride content linearly increase with the stress level in the tensile zone, while linearly decrease in the compressive zone, and the change is more obvious in the tensile zone. At stress levels of 15%, 30%, and 45%, the diffusion depth in the tensile zone increases by 11.4%, 36.6%, and 43.5%, respectively, and the increased ratios of chloride content are 1.2%, 11.2%, and 19.4%. There is no significant synergistic effect between stress and calcium leaching on chloride diffusion depth, but it is obvious on chloride content, especially when the tensile stress level is below 15% and the compressive stress level is above 30%, for which the differences caused by considering the synergistic effect or not are approximately 6% and 15%, respectively.

A novel strategy of concrete monitoring: The application of the integrated sensing element (ISE)

This study strategically provides an innovative pattern for concrete monitoring at the service and deterioration stages by the integrated sensing element (ISE). The advantage of the ISE is that it can independently respond to loading variation and cooperate with other sensors. The results show that the ISE can independently identify the cracking state, monitor stress conditions, and distinguish the creep behavior of concrete with different compressive strength levels. By applying this novel monitoring pattern, the relationships between stress and relative velocity change (∆v/v) can be accurately traced; meanwhile, concrete with different creep degrees can be identified. Additionally, by tracing the de-correlation coefficients (Kd), this study also reveals that the binding behavior between sensors and concrete has a significant impact on signal variation. Specifically, the maximum Kd value derived from the signal of ISE at the loading process (46.5% of the maximum uniaxial compressive strength) is lower than 0.1, while that value derived from the signal of the conventional contact transducers can exceed 0.5. At a short-time fixed loading experiment, the Kd values derived from the signal of ISE show no significant increasing trend.

MetaABR: A Meta-Learning Approach on Adaptative Bitrate Selection for Video Streaming

Video streaming is one of the most popular Internet applications that makes up a large amount of Internet traffic. A fundamental mechanism in video streaming is adaptive bitrate (ABR) selection which decides the proper compression level for each chunk of a video to optimize the users' quality of experience (QoE). The existing ABR algorithms require significant tuning and do not generalize to diverse network conditions and personalized QoE objectives. In this paper, we propose a novel framework for meta-learning based ABR design and discuss challenges of deploying learning based ABR mechanism in real-world video streaming systems. We utilize the proposed framework to design MetaABR, a novel adaptive bitrate selection algorithm based on meta-reinforcement learning to maximize users' QoE. By jointly training multiple learning tasks with a shared meta-critic, it can provide transferrable meta-knowledge to supervise bitrate selection across tasks, and can be applied to efficiently learn a new task in unseen environment with only a few trials. We implement MetaABR on an emulation platform which connects to the Linux network protocol stack through virtual network interfaces. Extensive experiments based on real-world traces and wireless testbed show that MetaABR achieves the best comprehensive QoE compared with the state-of-the-art ABR algorithms in a variety of network environments.

A simple probabilistic neural network for machine understanding

We discuss the concept of probabilistic neural networks with a fixed internal representation being models for machine understanding. Here, ‘understanding’ is interpretted as the ability to map data to an already existing representation which encodes an a priori organisation of the feature space. We derive the internal representation by requiring that it satisfies the principles of maximal relevance and of maximal ignorance about how different features are combined. We show that, when hidden units are binary variables, these two principles identify a unique model—the hierarchical feature model—which is fully solvable and provides a natural interpretation in terms of features. We argue that learning machines with this architecture possess a number of interesting properties, such as the continuity of the representation with respect to changes in parameters and data, the possibility of controlling the level of compression and the ability to support functions that go beyond generalisation. We explore the behaviour of the model with extensive numerical experiments and argue that models in which the internal representation is fixed reproduce a learning modality which is qualitatively different from that of traditional models, such as restricted Boltzmann machines.

Experimental investigation on temperature-dependent effective thermal conductivity of ceramic fiber felt

This paper presents a method to invert the effective thermal conductivity of ceramic fiber felt under high temperatures using experimentally measured specific heat capacity, density, and transient temperature data. The method combines the solution of the heat transfer equation with an inversion method based on real-valued genetic algorithm (GA) optimization, and 11 target parameters can be simultaneously inverted with one experimental dataset. The effective thermal conductivities of ceramic fiber felt were obtained by inversion under ambient pressures of 2 Pa and 100 kPa, compression ratios of 0.8–1.0, and temperature ranges of 295∼1273 K. The results indicates that the effective thermal conductivities of ceramic fiber felt derived from the inversion method are in concurrence with the outcomes of the steady state method. The effective thermal conductivities of the ceramic fiber felt range from 0.069 to 0.321 W m−1 K−1. It is observed that the effective thermal conductivity increases with higher temperature, and decreases with growing compression ratio. The impact of ambient pressure on effective thermal conductivity is linked to the level of compression.

Experimental Study on Seismic Performance of Prefabricated Monolithic Concrete–Polystyrene Panel Composite Wall Panels

A normal composite wall panel is a structural component composed of polystyrene insulation boards and concrete surface layers reinforced with steel wire mesh. It can be entirely prefabricated in a factory or constructed with the concrete surface layers cast on-site. A novel prefabricated monolithic concrete–polystyrene panel composite wall panel (CPC wall panel) is proposed in this study. The CPC panel features a middle part that is prefabricated in the factory while the reinforced concrete regions at its two side ends are cast on-site. To evaluate the seismic performance of the wall panel, 18 CPC specimens were designed, manufactured, and quasi-statically tested, through which the structural behaviors, failure mode, and load-bearing capacity were studied. In addition, the influences of the height-to-width ratio and the vertical compressive stress level on the seismic performance of the CPC panels were also investigated. The test results showed that the connectors spaced at 400 mm × 500 mm could ensure the concrete layers on both sides of the polystyrene board worked collectively under seismic conditions. When subjected to lateral loads, the interface between the newly poured concrete and the existing concrete exhibited good bonding. Moreover, the failure mode of the CPC wall panel was largely correlated to the height-to-width ratio that, for specimens having four steel bars of 12 mm diameter and a height-to-width ratio greater than 1, the flexural failure was initially developed, followed by diagonal shear failure. In specimens with a height-to-width ratio of 1, flexural and diagonal shear failures occurred almost simultaneously. For specimens with a height-to-width ratio of less than 1, the final diagonal shear failure was predominant. The longitudinal reinforcing bars at the two ends of the CPC panels could effectively improve their lateral load-bearing capacity, with the enhancement influenced by the height-to-width ratio, the vertical load applied to the wall panel, and the cross-sectional area of the steel bars. In practice, the lateral load-bearing capacity of the CPC panel can be conservatively evaluated using the calculation method of the reinforced concrete shear walls. Finally, the ductility of the CPC specimens was affected by the height-to-width ratio and the axial compressive stress level, such that the specimens with a larger height-to-width ratio and lower axial compressive stress exhibited better ductility.