507 research outputs found
Achieving full diversity in multi-antenna two-way relay networks via symbol-based physical-layer network coding
No full textThis paper considers physical-layer network coding (PNC) with M-ary phase-shift keying (MPSK) modulation in two-way relay channel (TWRC). A low complexity detection technique, termed symbol-based PNC (SPNC), is proposed for the relay. In particular, attributing to the outer product operation imposed on the superposed MPSK signals at the relay, SPNC obtains the network-coded symbol (NCS) straightforwardly without having to detect individual symbols separately. Unlike the optimal multi-user detector (MUD) which searches over the combinations of all users’ modulation constellations, SPNC searches over only one modulation constellation, thus simplifies the NCS detection. Despite the reduced complexity, SPNC achieves full diversity in multi-antenna relay as the optimal MUD does. Specifically, antenna selection based SPNC (AS-SPNC) scheme and signal combining based SPNC (SC-SPNC) scheme are proposed. Our analysis of these two schemes not only confirms their full diversity performance, but also implies when SPNC is applied in multi-antenna relay, TWRC can be viewed as an effective single-input multiple-output (SIMO) system, in which AS-PNC and SC-PNC are equivalent to the general AS scheme and the maximal-ratio combining (MRC) scheme. Moreover, an asymptotic analysis of symbol error rate (SER) is provided for SC-PNC considering the case that the number of relay antennas is sufficiently large
Functionalisation of Liquid Metal Droplets by Surface and Interface Engineering and Electrification
No full textLiquid metals, particularly gallium-based alloys, have attracted increasing attention as a class of functional materials due to their excellent electrical conductivity, fluidity, and tunable surface chemistry. This thesis explores strategies to engineer tunable interfaces in liquid metals through alloy composition modulation and particle functionalisation, ultimately enabling the development of reconfigurable electroluminescent display systems.
In Chapters 1 and 2, the background and fundamental principles of gallium-based liquid metals, surface modulation, and electric discharge-induced electroluminescence are introduced through a critical review of relevant literature.
In Chapter 3, the author investigates the influence of minor alloying elements (Sn, Bi, Zn) on the electrocapillarity and electrochemical surface behaviour of gallium (Ga). By systematically analysing how trace elements affect surface tension, wetting dynamics, and oxidation-induced structures, this study reveals the underlying mechanisms that govern surface reactivity and electric field responses in Ga-based liquid metals.
In Chapter 4, the author demonstrates a particle-functionalized liquid metal platform by embedding electroluminescent phosphor particles (e.g., ZnS:Cu) into the oxide shell of EGaIn droplets, forming liquid metal marbles. These marbles enable dynamic visualisation of electric discharge paths under applied voltage, offering a novel approach to spatially map and manipulate discharge trajectories.
In Chapter 5, building upon the discharge-path visualisation strategy established in Chapter 4, the author further develops a reconfigurable multi-colour display platform using phosphor-coated liquid metal marbles. This chapter extends the concept from single-colour discharge visualisation to full-spectrum, programmable colour display. By incorporating red, green, and blue phosphors in controlled ratios, additive colour mixing is achieved without the need for physically separated subpixels.
In Chapter 6, the thesis concludes by summarizing the major findings and outlining future research directions. The results collectively establish a unified interface engineering framework for gallium-based liquid metals, with potential applications ranging from fundamental electrochemical modulation to advanced soft optoelectronic systems
Molecular beam optical study of gold sulfide and gold oxide
No full textGold-sulfur and gold-oxygen bonds are key components to numerous established and emerging technologies that have applications as far ranging as medical imaging, catalysis, electronics, and material science. A major theoretical challenge for describing this bonding is correctly accounting for the large relativistic and electron correlation effects. Such effects are best studied in diatomic, AuX, molecules. Recently, the observed AuS electronic state energy ordering was measured and compared to a simple molecular orbital
diagram prediction\footnote{D. L. Kokkin, R. Zhang, T. C. Steimle, I. A. Wyse, B. W. Pearlman and T. D. Varberg, \textit {J. Phys. Chem. A.}, {\textbf{119(48)}}, 4412, 2015.}. Here we more thoroughly investigate the nature of the electronic states of both AuS and AuO from the analysis of high-resolution (FWHMMHz) optical Zeeman spectroscopy of the (0,0)\textit {B}\textit {X} bands. The determined fine and hyperfine parameters for the \textit {B} state of AuO differ from those extracted from the analysis of a hot, Doppler-limited, spectrum\footnote{L. C. O'Brien, B. A. Borchert, A. Farquhar, S. Shaji, J. J. O'Brien and R. W. Field, \textit {J. Mol. Spectrosc.}, {\textbf{252(2)}}, 136, 2008.}. It is demonstrated that the nature of the \textit {B} states of AuO and AuS are radically different. The magnetic tuning of AuO and AuS indicates that the \textit {B} states are heavily contaminated.Made available in DSpace on 2017-01-26T21:39:46Z (GMT). No. of bitstreams: 3
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Previous issue date: 2016-06-2
Stroking through electrolyte: liquid metal droplet propulsion through pulse time modulation
No full textActive droplets play important roles in microfluidics, robotics, and micro-electromechanical systems. As a special class of active droplets that are conductive, reactive, and of high surface tension, liquid metal droplets (LMDs) can be driven by electric-field-induced surface (Marangoni) flows to function as reconfigurable components in actuators, sensors, catalytic reactors, and antennas. Stimulating LMDs using an electric field induces concurrent electro-hydrodynamic flows and electrochemical surface oxidation (passivation). It is however difficult to decouple these two effects which brings complexity in controlling LMD motions. To address this challenge, pulse time modulation (PTM) signals are used. PTM enables controlled LMD displacement by propelling the droplets forward during the voltage-on phases and facilitating surface recovery from oxidation during the voltage-off phases. Counterintuitively, by taking such intermittent “rests”, the LMDs effectively inhibit the unfavorable impact of oxidation, granting high motion controllability. Combining high-speed imaging, motion tracking, machine learning, and electrochemical analysis, the study reveals how electro-hydrodynamic flows and surface oxide formation/dissolution interplay to generate well-defined motion regimes. The study further develops a quasi-analytical model to describe droplet motions and designs a rotary LMD motor to showcase the versatility of the approach. This work provides the fundamental framework and viable strategy for designing innovative liquid metal-based systems.</p
Impact of Minor Alloy Components on the Electrocapillarity and Electrochemistry of Liquid Metal Fractals
No full textExploring and controlling surface tension‐driven phenomena in liquid metals may lead to unprecedented possibilities for next‐generation microfluidics, electronics, catalysis, and materials synthesis. In pursuit of these goals, the impact of minor constituents within liquid alloys is largely overlooked. Herein, it is showed that the presence of a fraction of solute metals such as tin, bismuth, and zinc in liquid gallium can significantly influence their electrocapillarity and electrochemistry. The instability‐driven fractal formation of liquid alloy droplets is investigated with different solutes and reveals the formation of distinctive non‐branched droplets, unstable fractals, and stable fractal modes under controlled voltage and alkaline solution conditions. In their individually unique fractal morphology diagrams, different liquid alloys demonstrate significantly shifted voltage thresholds in transition between the three fractal modes, depending on the choice of the solute metal. Surface tension measurements, cycle voltammetry and surface compositional characterizations provide strong evidence that the minor alloy components drastically alter the surface tension, surface electrochemical oxidation, and oxide dissolution processes that govern the droplet deformation and instability dynamics. The findings that minor components are able to regulate liquid alloys’ surface tensions, surface element distributions and electrochemical activities offer great promises for harnessing the tunability and functionality of liquid metals
Robust Lane Detection through Self Pre-training with Masked Sequential Autoencoders and Fine-tuning with Customized PolyLoss
No full textLane detection is crucial for vehicle localization which makes it the foundation for automated driving and many intelligent and advanced driving assistant systems. Available vision-based lane detection methods do not make full use of the valuable features and aggregate contextual information, especially the interrelationships between lane lines and other regions of the images in continuous frames. To fill this research gap and upgrade lane detection performance, this paper proposes a pipeline consisting of self pre-training with masked sequential autoencoders and fine-tuning with customized PolyLoss for the end-to-end neural network models using multi-continuous image frames. The masked sequential autoencoders are adopted to pretrain the neural network models with reconstructing the missing pixels from a random masked image as the objective. Then, in the fine-tuning segmentation phase where lane detection segmentation is performed, the continuous image frames are served as the inputs, and the pre-trained model weights are transferred and further updated using the backpropagation mechanism with customized PolyLoss calculating the weighted errors between the output lane detection results and the labeled ground truth. Extensive experiment results demonstrate that, with the proposed pipeline, the lane detection model performance on both normal and challenging scenes can be advanced beyond the state-of-the art results, while the training time can be substantially shortened
Education as Wound and Witness: A Narrative Across Four Generations of Chinese Women
No full textThis article offers a gentle yet profound meditation on a family history that spans over a century, beginning with a long farewell to the author’s maternal grandmother, Laolao. Through the experiences of four generations of women in a Chinese family, the author presents a historical lens to examine the meaning of education within a broader sociocultural context. The author's mother, who received what was considered a modern education, emerges as the most disconnected and, in the author’s words, the most broken among the four generations.
The article critically explores the unintended consequences of education when wielded as a tool of dominance, highlighting how, rather than liberating, it can dehumanize and wound. Yet, amidst the rupture, the author offers a path toward reconciliation through the quiet power of seeing. By bearing witness to the past of an individual, a family, and even a society, one may awaken the capacity to forgive, to heal, and to reclaim agency.
Departing from traditional academic structure, this article unfolds through narrative. It begins with an intimate story and gradually zooms out, revealing a historical scroll that invites readers to embark on a shared journey of reflection and rediscovery. You are invited. Please be patient and enter the flow
Atari-HEAD: Atari Human Eye-Tracking and Demonstration Dataset
No full textVersion 4 of the dataset is available (Sep 19 2019)!
Note this version has significantly more data than Version 2.
Dataset description paper (full version) is available!
https://arxiv.org/pdf/1903.06754.pdf (updated Sep 7 2019)
Tools for visualizing the data is available!
https://github.com/corgiTrax/Gaze-Data-Processor
=========================== Dataset Description ===========================
We provide a large-scale, high-quality dataset of human actions with simultaneously recorded eye movements while humans play Atari video games. The dataset consists of 117 hours of gameplay data from a diverse set of 20 games, with 8 million action demonstrations and 328 million gaze samples. We introduce a novel form of gameplay, in which the human plays in a semi-frame-by-frame manner. This leads to near-optimal game decisions and game scores that are comparable or better than known human records. For every game frame, its corresponding image frame, the human keystroke action, the reaction time to make that action, the gaze positions, and immediate reward returned by the environment were recorded.
Q & A: Why frame-by-frame game mode?
Resolving state-action mismatch: Closed-loop human visuomotor reaction time is around 250-300 milliseconds. Therefore, during gameplay, state (image) and action that are simultaneously recorded at time step t could be mismatched. Action at time t could be intended for a state 250-300ms ago. This effect causes a serious issue for supervised learning algorithms, since label at and input st are no longer matched. Frame-by-frame game play ensures states and actions are matched at every timestep.
Maximizing human performance: Frame-by-frame mode makes gameplay more relaxing and reduces fatigue, which could normally result in blinking and would corrupt eye-tracking data. More importantly, this design reduces sub-optimal decisions caused by inattentive blindness.
Highlighting critical states that require multiple eye movements: Human decision time and all eye movements were recorded at every frame. The states that could lead to a large reward or penalty, or the ones that require sophisticated planning, will take longer and require multiple eye movements for the player to make a decision. Stopping gameplay means that the observer can use eye-movements to resolve complex situations. This is important because if the algorithm is going to learn from eye-movements it must contain all “relevant” eye-movements.
============================ Readme ============================
1. meta_data.csv: meta data for the dataset., including:
GameName: String. Game name. e.g., “alien” indicates the trial is collected for game Alien (15 min time limit). “alien_highscore” is the trajectory collected from the best player’s highest score (2 hour limit). See dataset description paper for details.
trial_id: Integer. One can use this number to locate the associated .tar.bz2 file and label file.
subject_id: Char. Human subject identifiers.
load_trial: Integer. 0 indicates that the game starts from scratch. If this field is non-zero, it means that the current trial continues from a saved trial. The number indicates the trial number to look for.
highest_score: Integer. The highest game score obtained from this trial.
total_frame: Number of image frames in the .tar.bz2 repository.
total_game_play_time: Integer. game time in ms.
total_episode: Integer. number of episodes in the current trial. An episode terminates when all lives are consumed.
avg_error: Float. Average eye-tracking validation error at the end of each trial in visual degree (1 visual degree = 1.44 cm in our experiment). See our paper for the calibration/validation process.
max_error: Float. Max eye-tracking validation error.
low_sample_rate: Percentage. Percentage of frames with less than 10 gaze samples. The most common reason for this is blinking.
frame_averaging: Boolean. The game engine allows one to turn this on or off. When turning on (TRUE), two consecutive frames are averaged, this alleviates screen flickering in some games.
fps: Integer. Frame per second when an action key is held down.
2. [game_name].zip files: these include data for each game, including:
*.tar.bz2 files: contains game image frames. The filename indicates its trial number.
*.txt files: label file for each trial, including:
frame_id: String. The ID of a frame, can be used to locate the corresponding image frame in .tar.bz2 file.
episode_id: Integer (not available for some trials). Episode number, starting from 0 for each trial. A trial could contain a single trial or multiple trials.
score: Integer (not available for some trials). Current game score for that frame.
duration(ms): Integer. Time elapsed until the human player made a decision.
unclipped_reward: Integer. Immediate reward returned by the game engine.
action: Integer. See action_enums.txt for the mapping. This is consistent with the Arcade Learning Environment setup.
gaze_positions: Null/A list of integers: x0,y0,x1,y1,...,xn,yn. Gaze positions for the current frame. Could be null if no gaze. (0,0) is the top-left corner. x: horizontal axis. y: vertical.
3. action_enums.txt: contains integer to action mapping defined by the Arcade Learning Environment.
============================ Citation ============================
If you use the Atari-HEAD in your research, we ask that you please cite the following:
@misc{zhang2019atarihead,
title={Atari-HEAD: Atari Human Eye-Tracking and Demonstration Dataset},
author={Ruohan Zhang and Calen Walshe and Zhuode Liu and Lin Guan and Karl S. Muller and Jake A. Whritner and Luxin Zhang and Mary M. Hayhoe and Dana H. Ballard},
year={2019},
eprint={1903.06754},
archivePrefix={arXiv},
primaryClass={cs.LG}
}
Zhang, Ruohan, Zhuode Liu, Luxin Zhang, Jake A. Whritner, Karl S. Muller, Mary M. Hayhoe, and Dana H. Ballard. "AGIL: Learning attention from human for visuomotor tasks." In Proceedings of the European Conference on Computer Vision (ECCV), pp. 663-679. 2018.
@inproceedings{zhang2018agil,
title={AGIL: Learning attention from human for visuomotor tasks},
author={Zhang, Ruohan and Liu, Zhuode and Zhang, Luxin and Whritner, Jake A and Muller, Karl S and Hayhoe, Mary M and Ballard, Dana H},
booktitle={Proceedings of the European Conference on Computer Vision (ECCV)},
pages={663--679},
year={2018}
}
</p
CT Image Reconstruction by Spatial-Radon Domain Data-Driven Tight Frame Regularization
No full textThis paper proposes a spatial-Radon domain computed tomography (CT) image reconstruction model based on data-driven tight frames (SRD-DDTF). The proposed SRD-DDTF model combines the idea of the joint image and Radon domain inpainting model of Dong, Li, and Shen [J. Sci. Compd., 54 (2013), pp. 333-349] and that of the data-driven tight frames for image denoising [J.-F. Cai, H. Ji, Z. Shen, and G.-B. Ye, Appl. Compd. Harmon. Anal., 37 (2014), p. 89-105]. It is different from existing models in that both the CT image and its corresponding high quality projection image are reconstructed simultaneously using sparsity priors by tight frames that are adaptively learned from the data to provide optimal sparse approximations. An alternative minimization algorithm is designed to solve the proposed model, which is nonsmooth and nonconvex. Convergence analysis of the algorithm is provided. Numerical experiments show that the SRD-DDTF model is superior to the model of Dong, Li, and Shen [J. Sci. Compd., 54 (2013), pp. 333-349] especially in recovering some subtle structures in the images.Thousand Talents Plan of ChinaSCI(E)[email protected]; [email protected]
A Comparative Study of Gold Bonding via Electronic Spectroscopy
No full textabstract: The bonding and electrostatic properties of gold containing molecules are highly influenced by relativistic effects. To understand this facet on bonding, a series of simple diatomic AuX (X=F, Cl, O and S) molecules, where upon bond formation the Au atom donates or accepts electrons, was investigated and discussed in this thesis.
First, the optical field-free, Stark, and Zeeman spectroscopic studies have been performed on AuF and AuCl. The simple polar bonds between Au and typical halogens (i.e. F and Cl) can be well characterized by the electronic structure studies and the permanent electric dipole moments, el. The spectroscopic parameters have been precisely determined for the [17.7]1, [17.8]0+ and X1+ states of AuF, and the [17.07]1, [17.20]0+ and X1+ states of AuCl. The el have been determined for ground and excited states of AuF and AuCl. The results from the hyperfine analysis and Stark measurement support the assignments that the [17.7]1 and [17.8]0+ states of AuF are the components of a 3 state. Similarly, the analysis demonstrated the [19.07]1 and [19.20]0+ states are the components of the 3 state of AuCl.
Second, my study focused on AuO and AuS because the bonding between gold and sulfur/oxygen is a key component to numerous established and emerging technologies that have applications as far ranging as medical imaging, catalysis, electronics, and material science. The high-resolution spectra were record and analyzed to obtain the geometric and electronic structural data for the ground and excited states. The electric dipole moment, el, and the magnetic dipole moment, m, has been the precisely measured by applying external static electric and magnetic fields. el andm are used to give insight into the unusual complex bonding in these molecules.
In addition to direct studies on the gold-containing molecules, other studies of related molecules are included here as well. These works contain the pure rotation measurement of PtC, the hyperfine and Stark spectroscopic studies of PtF, and the Stark and Zeeman spectroscopic studies of MgH and MgD.
Finally, a perspective discussion and conclusion will summarize the results of AuF, AuCl, AuO, and AuS from this work (bond lengths, dipole moment, etc.). The highly quantitative information derived from this work is the foundation of a chemical description of matter and essential for kinetic energy manipulation via Stark and Zeeman interactions. This data set also establishes a synergism with computation chemists who are developing new methodologies for treating relativistic effects and electron correlation.Dissertation/ThesisDoctoral Dissertation Chemistry 201
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