The shear response of thirteen slender geopolymer concrete (GPC) beams reinforced with basalt fiber reinforced polymer (BFRP) bars as longitudinal reinforcements without stirrups was investigated. ...Different fiber combinations were used to enhance the shear capacity of the beams, including (1) single type of macro-steel fibers (SF) or (2) macro-synthetic polypropylene fibers (PF), (3) hybridization of SF and micro-polyvinyl alcohol fibers (PVF) or (4) PF and micro- carbon fibers (CF). The experimental results indicated that the presence of SF yielded the greatest improvement in the cracking behavior, post-cracked stiffness, and shear capacity of the beams. The addition of 0.5% SF to the GPC and OPC beams increased the normalized shear strength most by 56% and 14%, respectively. The higher contribution of SF to the shear strength of GPC can be attributed to the superior adhesive bonding strength of fiber and GPC matrix. Despite being less effective than SF, adding PF also improves significantly the normalized shear strength up to 33% with 0.5% fiber content. The hybridization of SF and PVF showed a good synergy in enhacing the shear capacity. Meanwhile, the combination of PF and CF did not improve the shear strength but enhanced considerably the ductility of the beams. In addition, three analytical models were proposed to estimate the shear capacity of the SF reinforced concrete beams. The comparison of prediction and experimental results demonstrated the model derived from the modified compression field theory (MCFT) achieved the best correlation.
•Distinctive behaviour of GPC beams versus ordinary Portland Concrete (OPC) beams.•Effect of steel fiber on the flexural behaviour of GPC beams.•Analytical procedure to estimate the load-deflection ...curve of FRC beams.
This study investigates the flexural behaviour of geopolymer concrete (GPC) beams reinforced with steel fibers. The effects of the volume fraction and fiber length on the flexural behaviour of GPC beams are investigated. The distinctive behaviour of GPC beams versus ordinary Portland Concrete (OPC) beams is identified and discussed. Based on the experimental results, the GPC beams reinforced with steel fibers showed great improvement in the cracking resistance, serviceability, and ductility compared to the reference beams. The GPC beam without steel fibers failed in a very brittle manner while those reinforced with steel fibers experienced ductile failure. The load capacity of the GPC beams increased with the volume fraction of steel fiber up to 0.75%. Further increasing the fiber content to 1.5% showed a deterioration in the flexural behavior due to poor workability of GPC leading to worse fiber dispersion and orientation. The increase of fiber length up to 60 mm did not improve the moment capacity of the GPC beams owing to premature fiber fracture. An analytical procedure was proposed to estimate the load-deflection curve of the tested beams with good correlation between predictive and experimental results.
•Unveil reason for negative reaction force in drop-weight impact tests.•Discuss and recommendation for reliable measurement of impact force.•Discuss and recommendation for reliable measurement of ...reaction force.•Discuss and recommendation for data processing and interpretation.
The impact response of reinforced concrete (RC) beams has been intensively investigated by impact tests with various setups. Given the same impact energy, different setups of drop-weight impact tests might lead to different measurements and observations of identical RC beams including the impact force, reaction force and displacement, implying the obtained impact test results depend on not only the impact energy and structure itself, but also the test setups. Therefore, it is essential to understand the measurement accuracy, reliability, and controllability of drop-weight impact tests for a successful impact test design and interpretation of test results on RC beams. This study examines the effects of various test setups and critical factors on the impact response of RC beams. Recommendations for the processing and interpretation of test results with respect to the configuration of the test setup, including the location of load cells, mass and shape of the impact head, interlayer, and boundary condition are made for drop-weight tests. The mechanism of the negative reaction force often observed in impact tests has been unveiled for a better understanding of the impact problem.
•First study on the impact behaviour of fiber reinforced geopolymer beams.•Using fibers mitigated the concrete crushing damage and cover spalling.•Increasing fibre dosage shifted response from ...shear-flexure to flexural dominance.•Impact, reaction force, and displacement were slightly affected by fibre inclusion.
Increased number of studies of the performances of geopolymer concrete (GPC) structures reinforced with fibre reinforced polymer (FRP) under static loadings have been reported recently, aiming at developing an alternative of the traditional constructions with ordinary Portland concrete (OPC) and steel reinforcement because GPC is a sustainable construction material and FRP is corrosion resistant. Study of the dynamic performance of GPC structures reinforced with FRP is, however, very limited. This study experimentally investigates the impact response of ambient cured GPC beams reinforced with different types of fibres and basalt fibre reinforced polymer (BFRP) bars. Four GPC beams reinforced with steel fibres or synthetic fibres and two control beams made of GPC and OPC without fibre reinforcement were cast and cured under ambient conditions. The volume fraction of fibres varied from 0 to 0.5% were used in concrete mix and BFRP bars and stirrups were used for longitudinal and transverse reinforcements respectively. All the beams were tested under drop-weight impact and after impact tests, the damaged beams were monotonically loaded under three-point bending tests to obtain the residual strength. The experimental results demonstrate that the presence of fibres reduced damages in the crushing zone and mitigated the concrete cover spalling at the bottom of the beams. Also, increasing the volume fraction of fibres shifted the crack patterns and failure modes of the beams from shear-flexure to flexural dominance. However, adding fibres had insignificant effects on the peak impact force, reaction forces, and mid-span displacement. The findings from the residual strength tests indicate that the beams with higher fibre dosage which failed in flexural dominance mode under impact loading have smaller residual strength, different from the expected performance observed in the fibre reinforced concrete beams under static load. Discussions are provided to explain these observations.
Chest radiography is one of the most common types of diagnostic radiology exams, which is critical for screening and diagnosis of many different thoracic diseases. Specialized algorithms have been ...developed to detect several specific pathologies such as lung nodules or lung cancer. However, accurately detecting the presence of multiple diseases from chest X-rays (CXRs) is still a challenging task. This paper presents a supervised multi-label classification framework based on deep convolutional neural networks (CNNs) for predicting the presence of 14 common thoracic diseases and observations. We tackle this problem by training state-of-the-art CNNs that exploit hierarchical dependencies among abnormality labels. We also propose to use the label smoothing technique for a better handling of uncertain samples, which occupy a significant portion of almost every CXR dataset. Our model is trained on over 200,000 CXRs of the recently released CheXpert dataset and achieves a mean area under the curve (AUC) of 0.940 in predicting 5 selected pathologies from the validation set. This is the highest AUC score yet reported to date. The proposed method is also evaluated on the independent test set of the CheXpert competition, which is composed of 500 CXR studies annotated by a panel of 5 experienced radiologists. The performance is on average better than 2.6 out of 3 other individual radiologists with a mean AUC of 0.930, which ranks first on the CheXpert leaderboard at the time of writing this paper.
Non-independent and identically distributed (non-IID) data distribution among clients is considered as the key factor that degrades the performance of federated learning (FL). Several approaches to ...handle non-IID data, such as personalized FL and federated multitask learning (FMTL), are of great interest to research communities. In this work, first, we formulate the FMTL problem using Laplacian regularization to explicitly leverage the relationships among the models of clients for multitask learning. Then, we introduce a new view of the FMTL problem, which, for the first time, shows that the formulated FMTL problem can be used for conventional FL and personalized FL. We also propose two algorithms <inline-formula> <tex-math notation="LaTeX">\textsf {FedU} </tex-math></inline-formula> and decentrali- zed <inline-formula> <tex-math notation="LaTeX">\textsf {FedU} </tex-math></inline-formula> (<inline-formula> <tex-math notation="LaTeX">\textsf {dFedU} </tex-math></inline-formula>) to solve the formulated FMTL problem in communication-centralized and decentralized schemes, respectively. Theoretically, we prove that the convergence rates of both algorithms achieve linear speedup for strongly convex and sublinear speedup of order <inline-formula> <tex-math notation="LaTeX">1/2 </tex-math></inline-formula> for nonconvex objectives. Experimentally, we show that our algorithms outperform the conventional algorithm FedAvg, FedProx, SCAFFOLD, and AFL in FL settings, MOCHA in FMTL settings, as well as pFedMe and Per-FedAvg in personalized FL settings.
Background Surgical innovations are introduced to improve “recovery,” a complex construct often operationalized by the use of patient-reported outcomes. The minimal clinically important difference ...(MCID) is the smallest change in an outcome sufficiently important to influence management and is crucial for designing and interpreting comparative effectiveness trials. Our objective was to generate MCID estimates for three postoperative recovery metrics. Methods Prospectively collected data on two cohorts of 281 and 130 adult patients undergoing abdominal surgery were analyzed. At each of three visits, patients had completed the 36-Item Short Form Survey from the RAND Medical Outcomes Study (SF-36) and either Community Healthy Activities Model Program for Seniors (CHAMPS) or the 6-minute walk test (6MWT). The MCID was estimated with an anchor-based approach with random effects linear regression models. Patients' rating of their own health was used to predict SF-36 domain, CHAMPS, and 6MWT scores. Results are reported as MCID (95% confidence interval). Results On the SF-36 domains analyzed, MCIDs were consistently smaller for patients rating their health as “excellent” or “very good” (from 8 6–9 to 15 12–18) compared with those for patients rating their health as “fair” or “poor” (from 15 12–19 to 32 28–36). For CHAMPS, the MCID was 8 kcal/kg/week (7–9), and for the 6MWT, 14 meters (9–18). Conclusion Plausible MCIDs and ranges around each estimate are provided. These values should be considered when planning and interpreting abdominal surgery clinical trials where patient-reported outcomes are assessed.
•First study on shear behavior of ambient-cured Geopolymer concrete (GPC) beams reinforced with BFRP bars under impact load.•Shear capacities under static load are compared with the predications by ...CSA and ACI codes.•Effect of spiral and rectangular stirrups on the shear behavior of GPC beams.•The KCC model with the modified parameters to predict the behavior of GPC beams.•Parametric study on impact performance of BFRP reinforced GPC beam is conducted.
The use of fiber reinforced polymer (FRP) bars in GeoPolymer Concrete (GPC) structures has drawn increasing attention in recent years. The application of GPC with basalt fiber reinforced polymer (BFRP) reinforcements in replacing Ordinary Portland cement Concrete (OPC) and steel reinforcements leads to green and sustainable constructions. Currently, very limited studies have been conducted to investigate the performance of GPC beams reinforced with BFRP bars under static loads, but no study on their performance under impact loads has been reported yet in open literature. In this study, ambient-cured GPC beams reinforced with BFRP bars were designed, cast and tested under static and impact loads. The damage mode and quantitative results such as midspan deflection, reinforcement strain, and impact and reaction forces were recorded and analysed. Test results showed that spiral stirrups led to superior performance of the beams under both static and impact loads as compared to conventional rectangular stirrups. The commonly used concrete material model *Mat_072R3 in LS-DYNA was modified based on test data to model GPC material. With the modified GPC material model, numerical models were developed and calibrated against the impact test results. Parametric studies were carried out to investigate the influences of GPC material strength and longitudinal and stirrup reinforcement ratios on the performance of beams subjected to impact loads. It was also found that using steel bars as the compression reinforcements led to better performance because BFRP bars under shear and compression were vulnerable to splitting damage subjected to impact loads.
•Impact responses of fiber reinforced geopolymer beams.•Comparable impact behaviour of GPC and OPC beams.•Methods to estimate the imparted energy.•Effect of different contact conditions (hard vs ...rubber pad) on impact behaviour.
This study investigates the shear capacity of fibre-reinforced geopolymer concrete (GPC) beams subjected to impact loads. For easy examination of the shear capacities, GPC beams, as well as two reference beams made of ordinary Portland cement (OPC) based concrete, without stirrups were prepared and subjected to the drop-weight impact tests with different contact conditions (direct contact and rubber pad contact). In the case of the beams under direct contact, the failure mode was observed to be a purely diagonal shear failure. The change in concrete material from OPC concrete to GPC showed a marginal effect on the impact response of the beams. Adding fibres into the GPC matrix improved considerably the post-failure behaviour of the beams. The beams reinforced with fibres exhibited not only less concrete spalling and fragmentation but also much higher reaction forces and the second impulse of the impact force. However, the fibre reinforcement seemed to have only a minor effect on the local and contact stiffness of the beams and thus the first impulse of impact force of all the beams was quite similar. The fast Fourier transform (FFT) analysis showed that the adoption of rubber pad contact reduced the highest dominated frequency of impact force from 2.5 kHz to 0.5 kHz. Using rubber pad contact led to the change in the failure pattern of the beams from the purely diagonal shear to the flexure-shear combined failure. The methods used for estimating the imparted and absorbed energy were compared and evaluated. The analysis results demonstrated that the method based on the impact force vs displacement yielded inaccurate results when the inclination angle between the drop hammer and the beams increased. Therefore, this study suggests that the variation in the kinetic energy of the drop hammer should be used to calculate the imparted energy to the impacted beam.
Background
Little is known about how to best communicate with older adults about dietary behaviors and related factors in complex chronic disease care. Photo‐based communication could promote ...efficient information exchange and activate patients to effectively communicate their lived experiences. We conducted a pilot study to assess the feasibility and acceptability of a photo‐based patient‐clinician communication intervention to promote dietary discussions in geriatric primary care.
Methods
Older adult patients with 2+ concurrent chronic conditions received in‐person training on photo‐taking with a smartphone before taking photos in response to the prompt, “What aspects of your everyday life affect what you eat and how much you have to eat?” Patients then shared photos and their narratives with their primary care clinician during a clinic visit. Patients and clinicians completed separate audio‐recorded post‐visit interviews to assess perspectives on the intervention. Interview transcripts were analyzed using a thematic analysis approach.
Results
Fourteen patient‐clinician dyads completed the study. All except one patient‐clinician dyad (93%) completed the intervention as trained. 93% of patients and 86% of clinicians reported that they would “definitely” or “probably” be willing to engage in a future visit with photo‐sharing. Patients and clinicians shared similar perspectives on how sharing of photos during the visit enhanced communication and information exchange about dietary practices and other health‐related factors, influenced clinical recommendations made during the visits, and strengthened the patient‐clinician relationship.
Conclusion
Incorporation of a photo‐based patient‐clinician communication intervention to promote discussions regarding diet and other health‐related factors could be a patient‐centered strategy to help deliver comprehensive geriatric primary care.
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