YL

Y. Liu

info

Please Note

13 records found

Journal article (2026) - B. Tian, F. Hu, Y. Zhang, Y. Liu, N. Wang, J. Sun
Multiples propagate along longer paths than primaries and have been incorporated into reverse time migration (RTM) to enhance subsurface illumination. However, RTM of multiples often suffers from severe crosstalk artifacts caused by cross-correlations among unrelated multiple orders. Moreover, the conventional shot-domain RTM framework becomes computationally expensive when a large number of shots are involved. To address these challenges, we propose a hybrid-encoding-based RTM method for multiple imaging. Different multiple orders are first separated using a decomposition technique. Random-phase encoding is then applied to consecutive-order multiples to form supergathers, and linear time-delay encoding is used to compress these supergathers into a limited number of plane-wave gathers. The multiple-based image is subsequently obtained using the RTM operator. Compared with conventional shot-domain RTM of multiples, the proposed plane-wave-domain approach effectively suppresses crosstalk from chaotic-order interference while substantially reducing computational cost. Numerical experiments on the Pluto 1.5 model demonstrate that the method efficiently attenuates coherent crosstalk and improves the imaging of complex subsurface structures. ...
Conference paper (2024) - F. R.Segundo Sevilla, Y. Liu, E. Barocio, P. Korba, A. Zamora, D. Dotta, F. Bellizio, J. Cremer, J. Zhao, More authors...
This paper summarizes recent advancements on spatio-temporal data-driven and machine learning methods for static and dynamic security assessment, and their particular use cases. It is a collective effort of different research groups members of the IEEE Working Group on Big Data Analytics for Transmission Systems, to provide transmission system operators (TSOs) with innovative tools and ideas for their potential implementation. The algorithms presented here are classified as non-training and training approaches, namely spatio-temporal and machine learning based, considering as input time series from time domain simulations, and or synchrophasor data from wide-area monitoring systems. The efficacy of these algorithms is then evaluated in different IEEE benchmark models and using real system measurements from different countries. ...
Journal article (2023) - Y. Liu, W. Pan
Machine learning can be effectively applied in control loops to make optimal control decisions robustly. There is increasing interest in using spiking neural networks (SNNs) as the apparatus for machine learning in control engineering because SNNs can potentially offer high energy efficiency, and new SNN-enabling neuromorphic hardware is being rapidly developed. A defining characteristic of control problems is that environmental reactions and delayed rewards must be considered. Although reinforcement learning (RL) provides the fundamental mechanisms to address such problems, implementing these mechanisms in SNN learning has been underexplored. Previously, spike-timing-dependent plasticity learning schemes (STDP) modulated by factors of temporal difference (TD-STDP) or reward (R-STDP) have been proposed for RL with SNN. Here, we designed and implemented an SNN controller to explore and compare these two schemes by considering cart-pole balancing as a representative example. Although the TD-based learning rules are very general, the resulting model exhibits rather slow convergence, producing noisy and imperfect results even after prolonged training. We show that by integrating the understanding of the dynamics of the environment into the reward function of R-STDP, a robust SNN-based controller can be learned much more efficiently than TD-STDP. ...
Journal article (2023) - F.M. McCubbin, J.J. Barnes, K.E. Vander Kaaden, E.S. Steenstra, S.M. Elardo, R.A. Zeigler, M. Anand, Y. Liu, P. Ni, H. Hui, R.L. Klima, D. Burney, JMD Day, T. Magna, JW Boyce, R Tartése
Journal article (2023) - T. Stavenga, S. A. Khan, Y. Liu, P. Krogstrup, L. DiCarlo
Quantum hardware based on circuit quantum electrodynamics makes extensive use of airbridges to suppress unwanted modes of wave propagation in coplanar-waveguide transmission lines. Airbridges also provide an interconnect enabling transmission lines to cross. Traditional airbridge fabrication produces a curved profile by reflowing resist at elevated temperature prior to metallization. The elevated temperature can affect the coupling energy and even yield of pre-fabricated Josephson elements of superconducting qubits, tunable couplers, and resonators. We employ grayscale lithography to enable reflow and thereby reduce the peak temperature of our airbridge fabrication process from 200 to 150 °C and link this change to a substantial increase in the physical yield of transmon qubits with Josephson elements realized using Al-contacted InAs nanowires. ...
Conference paper (2023) - Z. Feng, R. Ferrari, J. W. van Wingerden, Y. Liu
Wind turbines may experience local weather perturbation, which is not taken into account by the commonly-used wind turbine simulation packages. Without this information, it is extremely challenging to evaluate the controller performance with regard to the effect of the variation of local atmospheric conditions. On the other side, it is too late and costly to wait until field test time. To fill this gap, in this paper, we develop a control-oriented turbine dynamic simulation framework to evaluate the controller performance considering the perturbation of local atmospheric conditions. This goal is achieved by integrating an internal wind turbine (IWT) model in the Weather Research and Forecasting (WRF) simulation tool. The proposed framework is implemented on a 5MW reference wind turbine, where the effects of the local atmospheric conditions are illustrated. The proposed WRF-IWT model are validated by comparing the results with those derived from the Fatigue, Aerodynamics, Structures, and Turbulence (FAST). ...
Review (2021) - A. Komashie, J. Ward, T. Bashford, T. Dickerson, G.K. Kaya, Y. Liu, I. Kuhn, A. Günay, K. Kohler, P.J. Clarkson
Objectives To systematically review the evidence base for a systems approach to healthcare design, delivery or improvement. Design Systematic review with meta-analyses. Methods Included were studies in any patients, in any healthcare setting where a systems approach was compared with usual care which reported quantitative results for any outcomes for both groups. We searched Medline, Embase, HMIC, Health Business Elite, Web of Science, Scopus, PsycINFO and CINAHL from inception to 28 May 2019 for relevant studies. These were screened, and data extracted independently and in duplicate. Study outcomes were stratified by study design and whether they reported patient and/or service outcomes. Meta-analysis was conducted with Revman software V.5.3 using ORs - heterogeneity was assessed using I 2 statistics. Results Of 11 405 records 35 studies were included, of which 28 (80%) were before-and-after design only, five were both before-and-after and concurrent design, and two were randomised controlled trials (RCTs). There was heterogeneity of interventions and wide variation in reported outcome types. Almost all results showed health improvement where systems approaches were used. Study quality varied widely. Exploratory meta-analysis of these suggested favourable effects on both patient outcomes (n=14, OR=0.52 (95% CI 0.38 to 0.71) I 2 =91%), and service outcomes (n=18, OR=0.40 (95% CI 0.31 to 0.52) I 2 =97%). Conclusions This study suggests that a systems approaches to healthcare design and delivery results in a statistically significant improvement to both patient and service outcomes. However, better quality studies, particularly RCTs are needed. PROSPERO registration number CRD42017065920. ...
Journal article (2021) - Y. Liu, T. Dickerson, F. Early, J. Fuld, C. Jiang, P.J. Clarkson
Background: Pulmonary rehabilitation (PR) is recommended for patients with COPD to improve their symptoms and quality of life. However, in the UK, only one in ten of those who need PR receive it and this might be inaccessible to people with disabilities. This study aims to inform improvements to PR service by identifying barriers to the uptake of PR in the COPD care journey in relation to patients’ capabilities that can affect their access to PR. Methods: An Inclusive Design approach with mixed methods was undertaken. Firstly, patients and healthcare professionals were interviewed to gather insight into their experiences of COPD care and map patients’ care journey. Secondly, an Exclusion Calculator was used to estimate service demand on patients’ capability and the proportion of population excluded from the service. Thirdly, a framework analysis was applied to guide data analysis to identify the challenges of accessing PR. Finally, proposed recommendations were refined with patients and healthcare professionals. Results: The overall capability-related exclusion number was very high (62.5%), and exclusion caused by limited mobility was the highest (50%) among the interviewees and even higher based on the population database. This suggests the importance of considering COPD patients’ capability-related needs to improve their access to care. Capability-related challenges for patients accessing PR such as poor mobility to transport and low vision impairing ability to read inhaler instructions were identified, as well as non-capability-related challenges such as patients’ perception about COPD and inability to access proper information. Recommendations were proposed to help patients to self-manage their COPD and access to PR. Conclusion: Lack of attention to COPD patients’ capability level in the delivery of PR may affect its uptake. Considering the capability-related needs of COPD patients and providing patients with reassurance, information, and support on their care journey could improve the uptake of PR. ...

Landscape architecture explorations in the Pearl River Delta, the Haringvliet and Pekalongan City through six MSc-graduation projects

This graduation studio explores the potential of a landscape-based regional design approach to contribute to more resilient coastal landscapes around the globe. Such an approach addresses the interaction between the natural and urban landscape throughout the scales of space and time. It takes the landscape as the basis for sustainable urban development and employs research through design as a strategy to explore the possibilities of landscape architecture principles for water-sensitive design, nature-based solutions, heritage protection, and socio-ecological inclusive development. This landscape approach is transdisciplinary in nature and exploits the power of design to address the complex challenges of our times while connecting long-term strategies and short-term interventions. The projects presented here showcase the wide range of possibilities of the landscape-approach in nature conservation, reduce flood risks, promote sustainable urban transformation and achieve a symbiosis between nature and culture. ...
Journal article (2020) - O. Pires, J. Azcona, F. Vittori, I. Bayati, S. Gueydon, A. Fontanella, Y. Liu, E. J. De Ridder, M. Belloli, J. W. Van Wingerden
The hybrid testing method developed by CENER for floating wind turbine scaled tests combining wind and waves (SIL) has been upgraded in order to introduce not only the wind turbine rotor thrust, but also the out-of-plane rotor moments (aerodynamic and gyroscopic). The former ducted-fan has been substituted by a multi-propellers actuator system. The new system has been completely developed, calibrated and used on a test campaign carried out at MARIN's Concept Basin. It was installed on a 1/50 scaled model of the DeepCwind 5MW semisubmersible turbine built by MARIN within the EU MARINET2/Call No.3 under ACTFLOW project framework. The control strategy of the floating turbine was developed by POLIMI and TUDELFT and integrated into the SIL numerical model. The experiment has proved a good behaviour of the enhanced SiL method. It has revealed that the relative importance of gyroscopic moments is low in comparison with the aerodynamic rotor moments in the considered cases. The results also show how rotor moments are particularly important in the floating turbine dynamics in cases with large rotor load imbalances such as situations where one blade fails to pitch. ...
Journal article (2020) - H. Li, X. Liang, A. Shrestha, Y. Liu, H. Heidari, J. Le Kernec, F. Fioranelli
This paper presents a hierarchical sensor fusion approach for human micro-gesture recognition by combining an Ultra Wide Band (UWB) Doppler radar and wearable pressure sensors. First, the wrist-worn pressure sensor array (PSA) and Doppler radar are used to respectively identify static and dynamic gestures through a Quadratic-kernel SVM (Support Vector Machine) classifier. Then, a robust wrapper method is applied on the features from both sensors to search the optimal combination. Subsequently, two hierarchical approaches where one sensor acts as 'enhancer' of the other are explored. In the first case, scores from Doppler radar related to the confidence level of its classifier and the prediction label corresponding to the posterior probabilities are utilized to maximize the static hand gestures classification performance by hierarchical combination with PSA data. In the second case, the PSA acts as an 'enhancer' for radar to improve the dynamic gesture recognition. In this regard, different weights of the 'enhancer' sensor in the fusion process have been evaluated and compared in terms of classification accuracy. A realistic cross-validation method is chosen to test one unknown participant with the model trained by data from others, demonstrating that this hierarchical fusion approach for static and dynamic gestures yields approximately 15% improvement in classification accuracy in the best cases. ...
Journal article (2019) - Y. Liu, T. Dickerson, P. Waddingham, P.J. Clarkson
Back pain is a very common health problem and affects people across the world. This study applies an Inclusive Design approach to a community-based back pain service to understand the challenges, in relation to patients' capabilities, that can affect their access to the service. It consisted of three steps: i) online surveys and interviews with physiotherapists and collected patients' personal online care stories to gather insight into their experiences within the back pain care journeys; ii) estimated services' demands made on patients when they access the service and identified the related challenges and iii) proposed recommendations that could address the challenges for patients to access the service. The study suggests an Inclusive Design approach could help identify capability-related challenges such as vision and memory which could affect people's access to back pain treatment. In addition, the application of the approach also uncovered some non-capability-related challenges. ...
Book chapter (2018) - Y. Liu, T. Dickerson, S. D. Waller, P. Waddingham, P. J. Clarkson
Inclusive Design is usually applied to consumer products and services; here we investigate if it can be applied to healthcare delivery services. Methods: A case study approach was used by applying Inclusive Design methods to a telephone 'Physio-Direct' service for patients with back pain. Online surveys and interviews with healthcare professionals were used to gather insight into the delivery of back pain care and to construct a task analysis of the patient care journey. The task analysis was used to estimate the service demand made on patients' capabilities. Finally, an exclusion calculator was used to estimate the proportion of a population excluded from the service. Results: The surveys (n = 30) and interviews (n = 4) showed that communication difficulties, patients' reduced capability, service misconceptions and difficulties in obtaining information were the main barriers, which prevented patients from accessing the service. Some tasks placed a high demand on the patients' capabilities. These included telephone assessment, waiting for a telephone response, memorising the verbal advice, understanding the posted exercise leaflets and doing the exercises. It was estimated that at least 15% of the British population are excluded from the 'Physio-Direct' service. Conclusion: Inclusive Design methods were applied to the 'Physio-Direct' service and demand on its users identified ways in which the service could be improved. This suggests that Inclusive Design may be a useful tool in improving healthcare service delivery. ...