| 1. |
- Tran, Quoc Cuong, et al.
(författare)
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Novel Ensemble Landslide Predictive Models Based on the Hyperpipes Algorithm : A Case Study in the Nam Dam Commune, Vietnam
- 2020
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Ingår i: Applied Sciences. - Switzerland : MDPI. - 2076-3417. ; 10:11
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Tidskriftsartikel (refereegranskat)abstract
- Development of landslide predictive models with strong prediction power has become a major focus of many researchers. This study describes the first application of the Hyperpipes (HP) algorithm for the development of the five novel ensemble models that combine the HP algorithm and the AdaBoost (AB), Bagging (B), Dagging, Decorate, and Real AdaBoost (RAB) ensemble techniques for mapping the spatial variability of landslide susceptibility in the Nam Dan commune, Ha Giang province, Vietnam. Information on 76 historical landslides and ten geo-environmental factors (slope degree, slope aspect, elevation, topographic wetness index, curvature, weathering crust, geology, river density, fault density, and distance from roads) were used for the construction of the training and validation datasets that are the prerequisites for building and testing the proposed models. Using different performance metrics (i.e., the area under the receiver operating characteristic curve (AUC), negative predictive value, positive predictive value, accuracy, sensitivity, specificity, root mean square error, and Kappa), we verified the proficiency of all five ensemble learning techniques in increasing the fitness and predictive powers of the base HP model. Based on the AUC values derived from the models, the ensemble ABHP model that yielded an AUC value of 0.922 was identified as the most efficient model for mapping the landslide susceptibility in the Nam Dan commune, followed by RABHP (AUC = 0.919), BHP (AUC = 0.909), Dagging-HP (AUC = 0.897), Decorate-HP (AUC = 0.865), and the single HP model (AUC = 0.856), respectively. The novel ensemble models proposed for the Nam Dan commune and the resultant susceptibility maps can aid land-use planners in the development of efficient mitigation strategies in response to destructive landslides.
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| 2. |
- Cuc, Nguyen Thi Thu, et al.
(författare)
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Hot water treatment prevents Aphelenchoides besseyi damage to Polianthes tuberosa crops in the Mekong Delta of Vietnam
- 2010
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Ingår i: Crop Protection. - 0261-2194. ; 29:6, s. 599-602
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Tidskriftsartikel (refereegranskat)abstract
- Polianthes tuberosa is a commercially valuable flower crop in the Mekong Delta of Vietnam that is propagated by the harvesting and planting of bulbs. The cultivation of P. tuberosa is infected by an endemic Aphelenchoides besseyi nematode that damages a high proportion of plants and persists within the bulbs. Here we report on the comparison of hot water and pesticide treatments as control methods to protect P. tuberosa from A. besseyi damage, and conclude that a hot water treatment consisting of soaking bulbs in water for 30 minutes at 57 °C is the most efficacious method to produce healthy flowers in a cost-effective manner.
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| 3. |
- Tran, Minh Quan, et al.
(författare)
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Coordination of Load Tap Changer and Distributed Energy Resources to Improve Long-term Voltage Stability
- 2022
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Ingår i: ENERGYCON 2022 - 2022 IEEE 7th International Energy Conference, Proceedings.
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Konferensbidrag (refereegranskat)abstract
- Along With the increased installation of the distributed energy resources (DER) in distribution system, long-term voltage stability at the transmission level can be improved if proper coordination is developed between DERs and the existing grid controllers, e.g., load tap changer (LTC). This paper analyzes the problem of long-term voltage instability and presenting possible countermeasures. The study summarizes essential aspects for modelling, including LTC, DERs, and especially voltage dependent load. A coordination between DERs and LTC is proposed to allocate better power supply, especially at the coupling points between transmission and distribution networks, i.e. primary substation. A case study is performed using a modified CIGRE medium-voltage benchmark network. The simulation results have shown that the coordination has substantially improved the long-term voltage stability in the way of using the reactive power support from DERs and increasing the LTC position instated of decreasing as the traditional method.
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| 4. |
- Tran, Minh Quan, et al.
(författare)
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MPC-Based Coordinated Voltage Control in LV Distribution Systems: A Case Study in Chalmers Campus Network
- 2023
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Ingår i: Conference Proceedings - 2023 IEEE Asia Meeting on Environment and Electrical Engineering, EEE-AM 2023.
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Konferensbidrag (refereegranskat)abstract
- This paper presents detailed analysis results of a model predictive control (MPC)-based coordinated voltage control demonstrated in a real low voltage network, the Chalmers campus in Sweden. First, the modeling of the MPC is presented, and the state space mode is obtained by linearization of the power flow equation around the operation point. Thus, an updated voltage vector in the grid is calculated through the sensitivity gain corresponding to reactive power deviation in the grid. Second, the developed MPC model is integrated into an Internet of Things (IoT) platform developed under the European FlexiGrid project. The state measurements in the Chalmers campus network are collected through the IoT platform as the input for the MPC model. Then, the optimal setpoints for distributed energy resources (DERs) are calculated and sent to DERs via the IoT platform. Lastly, onsite demonstration results are analyzed, showing the performance of the MPC-based voltage control in low-voltage distribution systems.
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| 5. |
- Tran, Minh Quan, et al.
(författare)
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Self-adaptive Controllers for Renewable Energy Communities Based on Transformer Loading Estimation
- 2022
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Ingår i: 2022 IEEE International Conference on Environment and Electrical Engineering and 2022 IEEE Industrial and Commercial Power Systems Europe, EEEIC / I and CPS Europe 2022.
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Konferensbidrag (refereegranskat)abstract
- In this paper, self-adaptive controllers for renewable energy communities based on data-driven approach are proposed to mitigate the voltage rise and transformer congestion at the community level. In the proposed approach, the transformer loading percentage is estimated by the trained data-driven model, which uses the extreme gradient boosting regression algorithm based on a measurement set acquired from critical coupling points of the communities. To avoid voltage rise issues, the droop control parameters (i.e., voltage threshold for P - V, Q - V curves) are adaptively tuned based on the solar irradiance availability and estimated transformer loading. The proposed approach has been tested in the IEEE European LV distribution network. Results showed that the control approach could effectively reduce 22.2 % of the total overloaded instances, while still keeping voltage magnitude in the operation range. This method can help DSOs manage voltage violation and congestion without further communication.
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| 6. |
- Tran, Trung Thai, et al.
(författare)
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Virtual Oscillator based Hierarchical Control Strategy for Multi-mode Operation of Microgrids
- 2022
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Ingår i: IEEE PES Innovative Smart Grid Technologies Conference Europe. ; 2022-October
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Konferensbidrag (refereegranskat)abstract
- One of the most important challenges in controlling a Microgrid is to enable a multi-mode operation with a smooth change from different modes. Recently, hierarchical control is considered as an effective approach to control and manage a Microgrid. This paper proposes a compatible hierarchical control strategy, leveraging the superior characteristics of Andronov-Hopf Oscillator, that enables both grid-connected and islanded operation, as well as seamless, reliable transition between operation modes. The proposed control strategy includes a PI-based Power Tracking Control loop, a Power Sharing Control loop using average consensus approach, a PR-based Synchronization Control, and a Fault Initiated Islanding Detection based on wideband, online impedance estimation. The results in MATLAB/Simulink are provided to validate the effectiveness of the proposed strategy.
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| 7. |
- Jha, Debesh, et al.
(författare)
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A comprehensive analysis of classification methods in gastrointestinal endoscopy imaging
- 2021
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Ingår i: Medical Image Analysis. - 1361-8415 .- 1361-8423. ; 70
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Tidskriftsartikel (refereegranskat)abstract
- Gastrointestinal (GI) endoscopy has been an active field of research motivated by the large number of highly lethal GI cancers. Early GI cancer precursors are often missed during the endoscopic surveillance. The high missed rate of such abnormalities during endoscopy is thus a critical bottleneck. Lack of attentiveness due to tiring procedures, and requirement of training are few contributing factors. An automatic GI disease classification system can help reduce such risks by flagging suspicious frames and lesions. GI endoscopy consists of several multi-organ surveillance, therefore, there is need to develop methods that can generalize to various endoscopic findings. In this realm, we present a comprehensive analysis of the Medico GI challenges: Medical Multimedia Task at MediaEval 2017, Medico Multimedia Task at MediaEval 2018, and BioMedia ACM MM Grand Challenge 2019. These challenges are initiative to set-up a benchmark for different computer vision methods applied to the multi-class endoscopic images and promote to build new approaches that could reliably be used in clinics. We report the performance of 21 participating teams over a period of three consecutive years and provide a detailed analysis of the methods used by the participants, highlighting the challenges and shortcomings of the current approaches and dissect their credibility for the use in clinical settings. Our analysis revealed that the participants achieved an improvement on maximum Mathew correlation coefficient (MCC) from 82.68% in 2017 to 93.98% in 2018 and 95.20% in 2019 challenges, and a significant increase in computational speed over consecutive years.
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| 8. |
- Zawahir, S, et al.
(författare)
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Standardised patient study to assess tuberculosis case detection within the private pharmacy sector in Vietnam
- 2021
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Ingår i: BMJ global health. - : BMJ. - 2059-7908. ; 6:10
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Tidskriftsartikel (refereegranskat)abstract
- Of the estimated 10 million people affected by (TB) each year, one-third are never diagnosed. Delayed case detection within the private healthcare sector has been identified as a particular problem in some settings, leading to considerable morbidity, mortality and community transmission. Using unannounced standardised patient (SP) visits to the pharmacies, we aimed to evaluate the performance of private pharmacies in the detection and treatment of TB.MethodsA cross-sectional study was undertaken at randomly selected private pharmacies within 40 districts of Vietnam. Trained actors implemented two standardised clinical scenarios of presumptive TB and presumptive multidrug-resistant TB (MDR-TB). Outcomes were the proportion of SPs referred for medical assessment and the proportion inappropriately receiving broad-spectrum antibiotics. Logistic regression evaluated predictors of SPs’ referral.ResultsIn total, 638 SP encounters were conducted, of which only 155 (24.3%) were referred for medical assessment; 511 (80·1%) were inappropriately offered antibiotics. A higher proportion of SPs were referred without having been given antibiotics if they had presumptive MDR-TB (68/320, 21.3%) versus presumptive TB (17/318, 5.3%; adjusted OR=4.8, 95% CI 2.9 to 7.8). Pharmacies offered antibiotics without a prescription to 89.9% of SPs with presumptive TB and 70.3% with presumptive MDR-TB, with no clear follow-up plan.ConclusionsFew SPs with presumptive TB were appropriately referred for medical assessment by private pharmacies. Interventions to improve appropriate TB referral within the private pharmacy sector are urgently required to reduce the number of undiagnosed TB cases in Vietnam and similar high-prevalence settings.
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