Browsing by Author "Hu, Yue"

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Influence of thermostatting on nonequilibrium molecular dynamics simulations of heat conduction in solids
(2019-12-21) Li, Zhen; Xiong, Shiyun; Sievers, Charles; Hu, Yue; Fan, Zheyong; Wei, Ning; Bao, Hua; Chen, Shunda; Donadio, Davide; Ala-Nissila, Tapio
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Nonequilibrium molecular dynamics (NEMD) has been extensively used to study thermal transport at various length scales in many materials. In this method, two local thermostats at different temperatures are used to generate a nonequilibrium steady state with a constant heat flux. Conventionally, the thermal conductivity of a finite system is calculated as the ratio between the heat flux and the temperature gradient extracted from the linear part of the temperature profile away from the local thermostats. Here, we show that, with a proper choice of the thermostat, the nonlinear part of the temperature profile should actually not be excluded in thermal transport calculations. We compare NEMD results against those from the atomistic Green's function method in the ballistic regime and those from the homogeneous nonequilibrium molecular dynamics method in the ballistic-to-diffusive regime. These comparisons suggest that in all the transport regimes, one should directly calculate the thermal conductance from the temperature difference between the heat source and sink and, if needed, convert it into the thermal conductivity by multiplying it with the system length. Furthermore, we find that the Langevin thermostat outperforms the Nosé-Hoover (chain) thermostat in NEMD simulations because of its stochastic and local nature. We show that this is particularly important for studying asymmetric carbon-based nanostructures, for which the Nosé-Hoover thermostat can produce artifacts leading to unphysical thermal rectification.
Is the spatial-temporal dependence model reliable for the short-term freight volume forecast of inland ports? A case study of the Yangtze River, China
(2021-09-08) Liu, Lei; Zhang, Yong; Chen, Chen; Hu, Yue; Liu, Cong; Chen, Jing
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The purpose of this study is to investigate whether spatial-temporal dependence models can improve the prediction performance of short-term freight volume forecasts in inland ports. To evaluate the effectiveness of spatial-temporal dependence forecasting, the basic time series forecasting models for use in our comparison were first built based on an autoregression integrated moving average model (ARIMA), a back-propagation neural network (BPNN), and support vector regression (SVR). Subsequently, combining a gradient boosting decision tree (GBDT) with SVR, an SVR- GBDT model for spatial-temporal dependence forecast was constructed. The SVR model was only used to build a spatial-temporal dependence forecasting model, which does not distinguish spatial and temporal information but instead takes them as data features. Taking inland ports in the Yangtze River as an example, the results indicated that the ports’ weekly freight volumes had a higher autocorrelation with the previous 1–3 weeks, and the Pearson correlation values of the ports’ weekly cargo volume were mainly located in the interval (0.2–0.5). In addition, the weekly freight volumes of the inland ports were higher depending on their past data, and the spatial-temporal dependence model improved the performance of the weekly freight volume forecasts for the inland river. This study may help to (1) reveal the significance of spatial correlation factors in ports’ short-term freight volume predictions, (2) develop prediction models for inland ports, and (3) improve the planning and operation of port entities.
The Open Brain Consent: Informing research participants and obtaining consent to share brain imaging data
(2021-05) Bannier, Elise; Barker, Gareth; Borghesani, Valentina; Broeckx, Nils; Clement, Patricia; Emblem, Kyrre E.; Ghosh, Satrajit; Glerean, Enrico; Gorgolewski, Krzysztof J.; Havu, Marko; Halchenko, Yaroslav O.; Herholz, Peer; Hespel, Anne; Heunis, Stephan; Hu, Yue; Hu, Chuan Peng; Huijser, Dorien; de la Iglesia Vayá, María; Jancalek, Radim; Katsaros, Vasileios K.; Kieseler, Marie Luise; Maumet, Camille; Moreau, Clara A.; Mutsaerts, Henk Jan; Oostenveld, Robert; Ozturk-Isik, Esin; Pascual Leone Espinosa, Nicolas; Pellman, John; Pernet, Cyril R.; Pizzini, Francesca Benedetta; Trbalić, Amira Šerifović; Toussaint, Paule Joanne; Visconti di Oleggio Castello, Matteo; Wang, Fengjuan; Wang, Cheng; Zhu, Hua
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Having the means to share research data openly is essential to modern science. For human research, a key aspect in this endeavor is obtaining consent from participants, not just to take part in a study, which is a basic ethical principle, but also to share their data with the scientific community. To ensure that the participants' privacy is respected, national and/or supranational regulations and laws are in place. It is, however, not always clear to researchers what the implications of those are, nor how to comply with them. The Open Brain Consent (https://open-brain-consent.readthedocs.io) is an international initiative that aims to provide researchers in the brain imaging community with information about data sharing options and tools. We present here a short history of this project and its latest developments, and share pointers to consent forms, including a template consent form that is compliant with the EU general data protection regulation. We also share pointers to an associated data user agreement that is not only useful in the EU context, but also for any researchers dealing with personal (clinical) data elsewhere.
A probabilistic analytics method to identify striking ship of ship-buoy contact at coastal waters
(2022-12-15) Liu, Lei; Zhang, Mingyang; Hu, Yue; Zhu, Wei; Xu, Sheng; Yu, Qing
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The identification of the ship that contact with the buoy can provide evidence for accident accountability. To this aim, the paper develops a probabilistic analytics method to evaluate the ship-buoy contact risk for the striking ship identification at the coastal areas by combining buoy domain and bounding box models. The method makes use of Automatic Identification System (AIS) data and navigational buoy data. Firstly, an AIS-based probabilistic buoy domain model is adopted for the determination of the safety boundary of the buoy to detect potential striking ships with a higher contact probability. Then, the bounding boxes of the navigational buoy and the detected potential striking ships are developed to detect the real striking ship by analyzing the interaction be-tween the ship bounding box and the buoy bounding box. Finally, the probabilistic analytics method is demonstrated in the South China Sea and validated using historical ship-buoy contact records. Results indicated that, from a probabilistic perspective, the safety buoy domain (critical boundary) existed with diverse distances dynamically. The proposed method could assist the identification of striking ships while aiding the definition of the safety buoy domain for preventing ship-buoy contacts. As a result, it has the potential to support the development of ship-buoy contact risk management and assist surveillance operators and master on board by improving their cognitive abilities in dangerous traffic scenarios.
Seeing industrial services through experience lens - Revealing a customer experience map to design for an experiential service in B2B context
(2016) Hu, Yue
School of Arts, Design and Architecture | Master's thesis
Nowadays, more and more companies become aware of the importance on experience investment, which not only brings customers pleasant and meaningful interactions during the business but also supports the company to formulate key brand differentiator compared to other competitors. Through the theoretical background research, it has been found that there is still a lack of academic studies and design cases about investigating industrial services with experiential thinking in business-to-business context. As a branch of UXUS research program, the thesis work relies on the case study in cooperation with Rolls-Royce Marine that deals with B2B transactions with customers. It depicts the exploration on how the customer experience map could be constructed under the product context ‘UUC azimuth thruster’ to support refining its industrial service through utilizing experience lens for the near future. Starting with project background introduction and study context definition, the objectives of this thesis have been framed as three research questions, which comprise of discovering the way to promote internal understanding on UUC customer journey as well as bringing the big picture of UUC customer service experience to in-house staff, and enhancing the focused service from the experiential aspect within a short-term outlook. After representing the literature review from both academic and practical domain, the in-house research is described about applying semi- structured interviews to map the industrial service process with touch points. It documents the identification regarding key service interactions and the internal standpoints about the customer service experience. The customer study process is explained then as collecting first-hand customer experience within the targeted UUC service scope, the information of customer journey context has been enriched at the same time. T o Integrate the internal and external study results, the first outcome of this thesis - UUC customer experience map has been uncovered to Rolls-Royce Marine. By identifying the key opportunity from the customer experience map, the thesis continues to illustrate the process of utilizing the experience goals for ideating the experience-driven actions that Rolls-Royce Marine could take on future service development. The developed concept is presented in detail as an experiential service story which has been further built up through information architecture, the flow of interaction and wireframes establishment, and Hi-Fi prototype creation. Lastly, the two outcomes of the thesis have been evaluated by internal experts to determine the directions for the following implementation. Through the in-house assessment, the customer experience map has been regarded as a valuable and meaningful tool that could help mapping the UUC customer journey and the related customer service experience. The re ned UUC service concept has also achieved quite positive feedback from the evaluators, which aims to boost the user experience both inside and outside the organization.
Size effect and transient phonon transport mechanism in approach-to-equilibrium molecular dynamics simulations
(2022-02-15) Sheng, Yufei; Hu, Yue; Fan, Zheyong; Bao, Hua
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Approach-to-equilibrium molecular dynamics (AEMD) is a widely used molecular dynamics (MD) method to extract thermal transport properties in different material systems. Despite the success in many applications, the thermal transport mechanism in AEMD is not well understood. Although AEMD can simulate larger domain than other MD variants, it still suffers from simulation domain size effect. In addition, the size effect is quite different from that of the nonequilibrium molecular dynamics (NEMD) simulations. In this paper, we reveal the phonon transport mechanism in AEMD by comparing the size-dependent thermal conductivity values of AEMD and phonon Boltzmann transport equation. We show that the simulation size of AEMD should be defined as half of the size in the conventional AEMD simulations with periodic boundary conditions. Also, the size effect in AEMD originates from ballistic phonon transport. Different from NEMD, some phonons with long mean-free paths do not contribute to the thermal conductivity, resulting in a smaller thermal conductivity than NEMD with the same size. Based on the phonon transport mechanism in AEMD, we suggest an extrapolation method for AEMD to obtain bulk thermal conductivity.
Unification of nonequilibrium molecular dynamics and the mode-resolved phonon Boltzmann equation for thermal transport simulations
(2020-04-15) Hu, Yue; Feng, Tianli; Gu, Xiaokun; Fan, Zheyong; Wang, Xufeng; Lundstrom, Mark; Shrestha, Som S.; Bao, Hua
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Nano-size confinement induces many intriguing non-Fourier heat conduction phenomena, such as nonlinear temperature gradients, temperature jumps near the contacts, and size-dependent thermal conductivity. Over the past decades, these effects have been studied and interpreted by nonequilibrium molecular dynamics (NEMD) and phonon Boltzmann transport equation (BTE) simulations separately, but no theory that unifies these two methods has ever been established. In this work, we unify these methods using a quantitative mode-level comparison and demonstrate that they are equivalent for various thermostats. We show that different thermostats result in different non-Fourier thermal transport characteristics due to the different mode-level phonon excitations inside the thermostats, which explains the different size-dependent thermal conductivities calculated using different reservoirs, even though they give the same bulk thermal conductivity. Specifically, the Langevin thermostat behaves like a thermalizing boundary in phonon BTE and provides mode-level thermal-equilibrium phonon outlets, while the Nose-Hoover chain thermostat and velocity rescaling method behave like biased reservoirs, which provide a spatially uniform heat generation and mode-level nonequilibrium phonon outlets. These findings explain why different experimental measurement methods can yield different size-dependent thermal conductivity. They also indicate that the thermal conductivity of materials can be tuned for various applications by specifically designing thermostats. The unification of NEMD and phonon BTE will largely facilitate the study of thermal transport in complex systems in the future by, e.g., replacing computationally unaffordable first-principles NEMD simulations with computationally less expensive spectral BTE simulations.