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- Hu, Jianfeng, et al.
(författare)
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A general mechanism of grain growth -I. Theory
- 2021
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Ingår i: Journal of Materiomics. - : Elsevier BV. - 2352-8478 .- 2352-8486. ; 7:5, s. 1007-1013
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Tidskriftsartikel (refereegranskat)abstract
- The behaviors of grain growth dominate the formation of the microstructure inside polycrystalline materials and thus strongly influence their practical performances. However, grain growth behaviors still remain ambiguous and thus lack a mathematical formula to describe the general evolution despite decades of efforts. Here, we propose a new migration model of grain boundary (GB) and further derive a mathematical expression to depict the general evolution of grain growth in the cellular structures. The expression incorporates the variables influencing growth rate (e.g. GB features, grain size and local grain size distribution) and thus reveals how the normal, abnormal and stagnant behaviors of grain growth occur in polycrystalline systems. In addition, our model correlates quantitatively GB roughening transition with grain growth behavior. The general growth theory may provide new insights into the GB thermodynamics and kinetics during the cellular structure evolution.
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| 2. |
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| 3. |
- Ren, Jun, et al.
(författare)
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Effect of silica fume on the mechanical property and hydration characteristic of alkali-activated municipal solid waste incinerator (MSWI) fly ash
- 2021
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Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 295
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Tidskriftsartikel (refereegranskat)abstract
- The incorporation of silica fume provides the solution to solve the low silica content of municipal solid waste incinerator fly ash, which hinders its utilisation in manufacturing alkali-activated solid waste incinerator fly ash. This paper reported the effect of silica fume and sodium silicate nature on the hardened properties, including compressive strength, hydration product and microstructure of alkali-activated municipal solid waste incinerator fly ash. In addition to characterising the property of municipal fly ash, the effect of silica fume in compressive strength of alkali-activated municipal solid waste incinerator fly ash under different sodium silicate dosage and modulus was investigated and its hydration products were determined by XRD and SEM. The results demonstrated that adding silica fume significantly improved the compressive strength by promoting the formation of C–S–H hydration product. Moreover, a higher sodium silicate content and modulus resulted in a higher compressive strength. The concentration of leachable heavy metals from harden specimen with 10% SF specimen was significantly reduced to the value which is much lower than the recommendation from Chinese standards.
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| 4. |
- Salvo, Gloria, et al.
(författare)
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Open vs minimally invasive radical trachelectomy in early-stage cervical cancer : International Radical Trachelectomy Assessment Study
- 2022
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Ingår i: American Journal of Obstetrics and Gynecology. - : Elsevier BV. - 0002-9378 .- 1097-6868. ; 226:1, s. 1-97
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Tidskriftsartikel (refereegranskat)abstract
- Background: Minimally invasive radical trachelectomy has emerged as an alternative to open radical hysterectomy for patients with early-stage cervical cancer desiring future fertility. Recent data suggest worse oncologic outcomes after minimally invasive radical hysterectomy than after open radical hysterectomy in stage I cervical cancer. Objective: We aimed to compare 4.5-year disease-free survival after open vs minimally invasive radical trachelectomy. Study Design: This was a collaborative, international retrospective study (International Radical Trachelectomy Assessment Study) of patients treated during 2005–2017 at 18 centers in 12 countries. Eligible patients had squamous carcinoma, adenocarcinoma, or adenosquamous carcinoma; had a preoperative tumor size of ≤2 cm; and underwent open or minimally invasive (robotic or laparoscopic) radical trachelectomy with nodal assessment (pelvic lymphadenectomy and/or sentinel lymph node biopsy). The exclusion criteria included neoadjuvant chemotherapy or preoperative pelvic radiotherapy, previous lymphadenectomy or pelvic retroperitoneal surgery, pregnancy, stage IA1 disease with lymphovascular space invasion, aborted trachelectomy (conversion to radical hysterectomy), or vaginal approach. Surgical approach, indication, and adjuvant therapy regimen were at the discretion of the treating institution. A total of 715 patients were entered into the study database. However, 69 patients were excluded, leaving 646 in the analysis. Endpoints were the 4.5-year disease-free survival rate (primary), 4.5-year overall survival rate (secondary), and recurrence rate (secondary). Kaplan-Meier methods were used to estimate disease-free survival and overall survival. A post hoc weighted analysis was performed, comparing the recurrence rates between surgical approaches, with open surgery being considered as standard and minimally invasive surgery as experimental. Results: Of 646 patients, 358 underwent open surgery, and 288 underwent minimally invasive surgery. The median (range) patient age was 32 (20–42) years for open surgery vs 31 (18–45) years for minimally invasive surgery (P=.11). Median (range) pathologic tumor size was 15 (0–31) mm for open surgery and 12 (0.8–40) mm for minimally invasive surgery (P=.33). The rates of pelvic nodal involvement were 5.3% (19 of 358 patients) for open surgery and 4.9% (14 of 288 patients) for minimally invasive surgery (P=.81). Median (range) follow-up time was 5.5 (0.20–16.70) years for open surgery and 3.1 years (0.02–11.10) years for minimally invasive surgery (P<.001). At 4.5 years, 17 of 358 patients (4.7%) with open surgery and 18 of 288 patients (6.2%) with minimally invasive surgery had recurrence (P=.40). The 4.5-year disease-free survival rates were 94.3% (95% confidence interval, 91.6–97.0) for open surgery and 91.5% (95% confidence interval, 87.6–95.6) for minimally invasive surgery (log-rank P=.37). Post hoc propensity score analysis of recurrence risk showed no difference between surgical approaches (P=.42). At 4.5 years, there were 6 disease-related deaths (open surgery, 3; minimally invasive surgery, 3) (log-rank P=.49). The 4.5-year overall survival rates were 99.2% (95% confidence interval, 97.6–99.7) for open surgery and 99.0% (95% confidence interval, 79.0–99.8) for minimally invasive surgery. Conclusion: The 4.5-year disease-free survival rates did not differ between open radical trachelectomy and minimally invasive radical trachelectomy. However, recurrence rates in each group were low. Ongoing prospective studies of conservative management of early-stage cervical cancer may help guide future management.
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| 5. |
- Zhang, Longbin, et al.
(författare)
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Ankle Joint Torque Estimation Using an EMG-Driven Neuromusculoskeletal Model and an Artificial Neural Network Model
- 2021
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Ingår i: IEEE Transactions on Automation Science and Engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 1545-5955 .- 1558-3783. ; 18:2, s. 564-573
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Tidskriftsartikel (refereegranskat)abstract
- In recent decades, there has been an increasing interest in the use of robotic powered exoskeletons to assist patients with movement disorders in rehabilitation and daily life. Providing assistive torque that compensates for the user’s remaining muscle contributions is a growing and challenging field within exoskeleton control. In this article, ankle joint torques were estimated using electromyography (EMG)-driven neuromusculoskeletal (NMS) model and an artificial neural network (ANN) model in seven movement tasks, including fast walking, slow walking, self-selected speed walking, and isokinetic dorsi/plantar flexion at 60◦/s and 90◦/s . In each method, EMG signals and ankle joint angles were used as input, the models were trained with data from 3-D motion analysis, and ankle joint torques were predicted. Six cases using different motion trials as calibration (for the NMS model)/training (for the ANN) were devised, and the agreement between the predicted and measured ankle joint torques was computed. We found that the NMS model could overall better predict ankle joint torques from EMG and angle data than the ANN model with some exceptions; the ANN predicted ankle joint torques with better agreement when trained with data from the same movement. The NMS model predicted ankle joint torque best when calibrated with trials during which EMG reached maximum levels, whereas the ANN predicted well when trained with many trials and types of movements. In addition, the ANN prediction may become less reliable when predicting unseen movements. Detailed comparative studies of methods to predict ankle joint torque are crucial for determining strategies for exoskeleton control. Note to Practitioners—In exoskeleton control for strength augmentation applied in military, industry, and healthcare applications, providing assistive torque that compensates for the user’s remaining muscle contributions, is a challenging problem. This article predicted the ankle joint torques by electromyography (EMG)-driven neuromusculoskeletal (NMS) model and an artificial neural network (ANN) model in different movements. To the best of our knowledge, this is the first study comparing joint torque prediction performance of EMG-driven model to ANN. In the EMG-driven NMS model, mathematical equations were formulated to reproduce the transformations from EMG signal generation and joint angles to musculotendon forces and joint torques. A three-layer ANN was constructed with an adaptive moment estimation (Adam) optimization method to learn the relationships between the inputs (EMG signals and joint angles) and the outputs (joint torques). In the experiments, we estimated ankle joint torques in gait and isokinetic movements and compared the performance of methods to predict ankle joint torque, relating to how the methods have been calibrated/trained. The detailed analysis of the methods’ performance in predicting ankle joint torque can significantly contribute to determining which model to choose, and under which circumstances, and, thus, be of great benefit for exoskeleton rehabilitation controller design.
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