455 research outputs found
Smarandache fantastic ideals of Smarandache BCI-algebras
No full textThe notion of Smarandache fantastic ideals is introduced, examples are given,
and related properties are investigated. Relations among Q-Smarandache fresh ideals, Q-Smarandache clean ideals and Q-Smarandache fantastic ideals are given. A characterization of a Q-Smarandache fantastic ideal is provided. The extension property for Q-Smarandache fantastic ideals is established
On symmetric bi-derivations of BCI-algebras
No full textThe notion of left-right (resp. right-left) symmetric bi-derivation of BCI-algebras is introduced and some related properties are investigated
Intuitionistic Fuzzy Points in Semigroups
No full textThe notion of intuitionistic fuzzy sets was introduced
by Atanassov as a generalization of the notion of fuzzy sets. Y.B. Jun
and S.Z. Song introduced the notion of intuitionistic fuzzy points.
In this paper we find some relations between the intuitionistic fuzzy
ideals of a semigroup S and the set of all intuitionistic fuzzy points
of S
Influential stimuli characteristics on SNR in SSVEP-based interfaces: Thesis report: researching different aspects that influence the SNR in SSVEP-based interfaces
No full textDifferent paradigms can be used to evoke brainwaves. These brainwaves can be interpreted as commands that can be used to control different applications. These frameworks that interpret the brainwaves are called brain-computer interfaces. Steady-state visually evoked potentials is one of these paradigms that uses external stimuli flickering at fixed frequencies to evoke brainwaves. This paradigm is fast to issue, is reliable, and needs no training time of the user. However, to be able to distinguish multiple commands it is important to distinguish between multiple commands reliably. The fundamental metric that determines the signal quality is the signal-to-noise ratio. The signal-to-noise ratio is measured in decibels and is the ratio in power between the signal that is evoked around the stimulus frequency and the power of some baseline, referred to as noise. To extract the power the discrete Fourier transform is calculated from the measured brainwaves. The brainwaves are measured in millivolts over time. These brainwaves can be recorded using implants in the head named intracortical or external, such as electroencephalography. External methods such as electroencephalography are much safer for the user. Important to recognize is that one of the contributing factors to signal-to-noise ratio are the characteristics of the external stimuli displayed. Research is still trying to figure out the exact relationship between stimuli characteristics and signal-to-noise ratio. However, the experiments of previous research lack the context of the gaze of the subjects to explain the electroencephalography recordings. In this research, this is attempted to be solved using eye tracking. Furthermore, there is a research gap in thethe scientific field surrounding signal-to-noise ratio and stimuli characteristics as the effect of surroundingstimuli on the measured signal-to-noise ratio of the target stimulus has never been investigated.This research attempted to solve these problems by performing 2 experiments with 6 participants. One experiment shows a single stimulus across various shapes (triangles, squares, and circles), colors (red, green, and white), frequencies (9, 13, 19, and 25Hz), and sizes (10.000, 20.000, 30.000 pixels). The other experiment simulates the natural environment of the external stimuli across the same frequencies, colors, and shapes. The natural environment of a single stimulus is actually surrounding stimuli at different frequencies, as applications often require the ability to distinguish between multiple different commands. Thus, to state the main research question: "What is the relationship between the stimuli characteristics and the measured SNR?".This question is answered by dissecting the effect that color, shape, size, frequency, and surrounding stimuli have on the signal-to-noise ratio. Dr.ir. Y.B. Eisma was the supervisor of S.T. van Vliet. Using his equipment the brainwaves were recorded at the UMC Amsterdam. https://github.com/SjoerdTimovanVliet/SSVEP_interface_thesisMechanical Engineering | Vehicle Engineering | Cognitive Robotic
Processes controlling the geochemical composition of the South China Sea sediments during the last climatic cycle
No full textAuthor Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Chemical Geology 257 (2008): 240-246, doi:10.1016/j.chemgeo.2008.10.002.Sediments of the upper 28.2 meters of Ocean Drilling Program (ODP) Site 1145 from
the northern South China Sea (SCS) were analyzed for their geochemical composition. Most
of the major and trace elements exhibit significant fluctuations at glacial-interglacial scales,
implying a close relation with regional and global climate change. Al-normalized elemental
ratios can be subdivided into three principal components (PC). PC1 (e.g., Ca/Al, Ba/Al, Sr/Al)
displays significant glacial-interglacial variation and is related to paleoproductivity in the
northern SCS. PC2 (e.g., K/Al, Mg/Al, Rb/Al) is associated with the degree of chemical
weathering in the source regions and shows little glacial-interglacial variation. PC3 (e.g.,
Ti/Al, Zr/Al) reflects the relative contribution of coarse- and fine-grained materials in the
terrigenous components of the SCS sediments, likely associated with changes in sea level and
monsoon-induced fluvial input. Spectral analyses indicate that paleoproductivity (i.e., Ba/Al)
in the South China Sea lags Hulu/Sanbao speleothem δ18O record (a indicator of annual
average meteoric precipitation) by 102° and Indian summer monsoon (multi-proxy stack) by
23° at the precession band, indicating a close relationship with the Indian summer monsoon.
However, the chemical weathering degree in the source area (PC2) is not sensitive to
monsoon-related changes at the precession band during the last climatic cycle.This study was supported by the NSFC to Y.B. Sun and the US NSF to D.W. Oppo (OCE 0502960) and S.C. Clemens (OCE 0352215)
Optimizing deep reinforcement learning policies for deteriorating systems considering ordered action structuring and value of information
No full textInspection and maintenance (I&M) optimization entails many sources of computational complexity, among others, due to high-dimensional decision and state variables in multi-component systems, long planning horizons, stochasticity of objectives and constraints, and inherent uncertainties in measurements and models. This paper studies how the above can be addressed within the context of constrained Partially Observable Markov Decision Processes (POMDPs) and Deep Reinforcement Learning (DRL) in a unified fashion. Special emphasis is paid on how ordered action structuring of I&M actions can be exploited to decompose the respective policy parametrizations in actor-critic DRL schemes, resulting into fully decoupled maintenance and inspection actors. It is shown that the Value of Information (VoI) is naturally utilized in such POMDP control frameworks, as directly associated with the DRL advantage functions that emerge in the gradient computations of the inspection policy parameters. Overall, the presented approach, following the natural flow of engineering decisions, results in new architectural configurations for policy networks, facilitating more efficient training, while alleviating further the dimensionality burdens related to combinatorial definitions of I&M actions. The efficiency of the methodology is demonstrated in numerical experiments of a structural system subject to corrosion, where the optimization problem is formulated to concurrently account for state and model uncertainties as well as long-term probability of failure exceedance constraints. Results showcase that the obtained DRL policies considerably outperform standard decision rules.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Structural Design & Mechanic
Model induction from data: Towards the next generation of computational engines in hydraulics and hydrology
No full textCivil Engineering and Geoscience
Long-term morphological modeling for Feiyun estuary with ESTMORF
No full textThe Feiyun River, with a length of 203 km and a catchment area of 3252 km2, is one of eight rivers in Zheijiang Province (see fig.1-1), China. It flows into the East China Sea in Shangwang of Ruian City. The source of Feiyun River is at Xialing located in the border between Zheijiang and Fujian Province. The tidal influence can reach up the river as far as Tanjiao located 59 km from the river mouth in the dry season during spring tide. The downstream river reach of Tanjiao is called the estuary reach mainly controlled by tidal flow, and its upstream is called river reach controlled by the basin runoff. The Feiyun Estuary connects the sea to Ruian harbour. There is an old and a new harbour zone near the Feiyun first bridge in Ruian City. The old harbour is only suitable for 300T to 500T ships. A quay berth for 1000T ship is in the new part. With the development of the economics and foreign trade of Ruian City, the harbour is developing rapidly. Therefore, it is necessary for local government to carry out the channel improvement of the Feiyun estuary. A lot of human interference's are going on / planned in the Feiyun estuary. In the upstream reach of the Feiyun River, the large scale Sanxi reservoir has been constructed and began to store water. Further the diversion from the Zhaoshadu reservoir will also be carried out. A bend cut-off project is also in schedule in order to improve the flood defence and create land for Ruian City. It is no doubt that all these human activities will have important effect on the long-term morphological development of the Feiyun estuary, especially for the navigation channel of the downstream section of the Feiyun estuary. Within the framework of Delft Cluster project Ecomorphology of Estuaries and Coasts, the longterm morphological development of the Feiyun estuary has been carried out with the ESTMORF model, which belongs to the hybrid class of the models. The impact of the bend cut-off in the Feiyun estuary, the construction of the Sanxi reservoir and the diversion project, to the long-term morphological development is studied.Hydraulic EngineeringCivil Engineering and Geoscience
Visual Attention in Human−Machine Interaction
No full textHumans are incapable of attending to everything at the same time. The serial nature of focused attention limits the information intake capacity of the perceptual system. This thesis deals with the measurement and modelling of visual attention distribution. It is examined whether measures of visual attention are predictive of task performance. The first chapter introduces the main topic of this thesis: the complex nature of modern technological systems, which feature many information sources that have to be monitored. Many psychological constructs have been proposed in the human factors literature that have alleged criterion validity for task performance. Here, task performance is regarded as the human’s ability to e.g., take over control of an automated system in potential critical situations. Contrary to the speculative nature of some of the Human- Factors constructs, this thesis sets out to capture performance in terms of objective measures of visual attention. Wickens’s (2008) Salience, Effort, Expectancy, Value (SEEV) model is introduced and discussed. This model is utilized for interpreting the eye-tracking results. Finally, a rationale for the topics in the thesis is provided. Chapters 2 through 4 of this thesis discuss and elaborate on Senders’s (1983) research in detail, by means of replication research and an extensive tutorial on his mathematical models. These chapters provide an empirical underpinning and conceptual understanding of the concept of visual attention. Chapters 5 through 8 discuss visual attention in light of Air Traffic Control (ATC) and automated driving, and are regarded as suitable cases for attention distribution measurement and task performance prediction. Chapter 9 investigates task performance and visual attention in a psychometric task: Inspection Time, which provides a good testbed for operationalizing the effect of attention on task performance. Chapter 10 concludes with a discussion on the topics in this thesis...Human-Robot Interactio
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