Sensorless Control of Switched-Flux Permanent Magnet Machines

This thesis investigates the sensorless control strategies of permanent magnet synchronous machines (PMSMs), with particular reference to switched-flux permanent magnet (SFPM) machines, based on high-frequency signal injection methods for low speed and standstill and the back-EMF based methods for medium and high speeds

A model of romance fiction search behavior

This poster describes a preliminary model of romance fiction search behavior based on grounded theory inspired interviews with avid romance readers. The model is composed of three elements: contextual factors, search goals, and selection strategies. The portrayed behavior characteristics and associations among contexts, goals, and strategies are based on at least one participant mention in our interview. We will continue to expand and verify the model in the following investigation with a hope to construct a theoretically and empirically sound model to analytically represent romance fiction readers' information and search behavior

On Task-Adaptive Pretraining for Dialogue Response Selection

Recent advancements in dialogue response selection (DRS) are based on the \textit{task-adaptive pre-training (TAP)} approach, by first initializing their model with BERT~\cite{devlin-etal-2019-bert}, and adapt to dialogue data with dialogue-specific or fine-grained pre-training tasks. However, it is uncertain whether BERT is the best initialization choice, or whether the proposed dialogue-specific fine-grained learning tasks are actually better than MLM+NSP. This paper aims to verify assumptions made in previous works and understand the source of improvements for DRS. We show that initializing with RoBERTa achieve similar performance as BERT, and MLM+NSP can outperform all previously proposed TAP tasks, during which we also contribute a new state-of-the-art on the Ubuntu corpus. Additional analyses shows that the main source of improvements comes from the TAP step, and that the NSP task is crucial to DRS, different from common NLU tasks.Comment: 6 pages, 4 figure

Stochastic recursions on directed random graphs

For a directed graph $G(V_n, E_n)$ on the vertices $V_n = \{1,2, \dots, n\}$, we study the distribution of a Markov chain $\{ {\bf R}^{(k)}: k \geq 0\}$ on $\mathbb{R}^n$ such that the $i$th component of ${\bf R}^{(k)}$, denoted $R_i^{(k)}$, corresponds to the value of the process on vertex $i$ at time $k$. We focus on processes $\{ {\bf R}^{(k)}: k \geq 0\}$ where the value of $R_i^{(k+1)}$ depends only on the values $\{ R_j^{(k)}: j \to i\}$ of its inbound neighbors, and possibly on vertex attributes. We then show that, provided $G(V_n, E_n)$ converges in the local weak sense to a marked Galton-Watson process, the dynamics of the process for a uniformly chosen vertex in $V_n$ can be coupled, for any fixed $k$, to a process $\{ \mathcal{R}_\emptyset^{(r)}: 0 \leq r \leq k\}$ constructed on the limiting marked Galton-Watson tree. Moreover, we derive sufficient conditions under which $\mathcal{R}^{(k)}_\emptyset$ converges, as $k \to \infty$, to a random variable $\mathcal{R}^*$ that can be characterized in terms of the attracting endogenous solution to a branching distributional fixed-point equation. Our framework can also be applied to processes $\{ {\bf R}^{(k)}: k \geq 0\}$ whose only source of randomness comes from the realization of the graph $G(V_n, E_n)$

Opinion dynamics on directed complex networks

We propose and analyze a mathematical model for the evolution of opinions on directed complex networks. Our model generalizes the popular DeGroot and Friedkin-Johnsen models by allowing vertices to have attributes that may influence the opinion dynamics. We start by establishing sufficient conditions for the existence of a stationary opinion distribution on any fixed graph, and then provide an increasingly detailed characterization of its behavior by considering a sequence of directed random graphs having a local weak limit. Our most explicit results are obtained for graph sequences whose local weak limit is a marked Galton-Watson tree, in which case our model can be used to explain a variety of phenomena, e.g., conditions under which consensus can be achieved, mechanisms in which opinions can become polarized, and the effect of disruptive stubborn agents on the formation of opinions

Investigating Thermal Comfort and User Behaviors in Outdoor Spaces: A Seasonal and Spatial Perspective

Numerous studies have examined the correlation between the number of attendants in a given outdoor environment and thermal indices to understand how the environmental planning has an impact on the users. However, extensive observations should be conducted to examine the detailed static and dynamic behavior patterns of users. We conducted dynamic observations at a stepped plaza to perform on-site measurements of the physical environment and observations of users behaviors, including their resting positions, movements, and stay durations. The results indicated that more people rested on the steps during the cool season than hot season. Compared to neutral temperatures, people demonstrated higher heat tolerance to the hot season. The results indicated that more than 75% of users preferred to remain in shaded areas and stayed longer than in the sunlight. The people tended to engage in static activities in environments that exhibit sufficient shading. The shaded areas were conducive to static activities as the summer grew hotter. The results verified that the people of Taiwan would avoid sunlight and desire shaded spaces based on their previous climate experiences and expectations, which can serve as a reference for outdoor space design to improve the usability and quality of open urban spaces

Sixth-harmonic back-EMF based sensorless control for switched-flux permanent magnet machine

In switched-flux permanent magnet (SFPM) machines, the 6th-harmonic back electromotive force (EMF) is dominant, whilst the 3rd-harmonic back-EMF is much smaller. This paper proposes several new position estimation methods for sensorless control based on the 6th-harmonic back-EMF. Firstly, by detecting the zero-crossings of the 6th-harmonic back-EMF with/without eliminating the influence of the 3rd-harmonic back EMF, the related rotor positions can be determined precisely at these zero-crossings. However, since the intermediate rotor positions need to be determined by linear interpretation between two zero-crossings, it only exhibits excellent performance under steady state. Furthermore, the continuous rotor position can be estimated from the proposed new observer by utilizing the combined signals of 6th-harmonic back-EMF and flux-linkage, together with a synchronous reference frame filter (SRFF) and harmonic elimination. Experimental validation show that (a) by eliminating the 3rd-harmonic back-EMF effect, the accuracy of the proposed 6th-harmonic back-EMF zero-crossings detection method can be improved, (b) SRFF is effective to minimize the influence of non-constant amplitudes of the 6th-harmonic backEMF and flux-linkage, (c) the comparison between the fundamental, the 3rd-harmonic back-EMF and the proposed method are presented in order to highlight the effectiveness of proposed control strategy under different operating conditions

Improved high-frequency carrier voltage measurement for position estimation of switched-flux permanent magnet machines

The conventional 12/10 stator/rotor poles switched-flux permanent magnet (SFPM) machine is usually based on all poles wound topology, each phase comprising four winding coils in series connection. However, alternate coils of the same phase have different machine saliency characteristics. Moreover, in order to measure the high-frequency (HF) carrier voltage, the mid-tapered winding wires can be utilized. Consequently, the machine saliencies can be measured separately from two parts of winding coil connections. This paper investigates the influences of machine saliencies on the sensorless rotor position estimations based on different sequence of winding coil connections, in which the primary saliency may contain some additional harmonics referring to the secondary saliency that will degrade the overall sensorless control operations. Furthermore, a simple compensation method is proposed to reduce the influence of multiple saliencies to achieve more accurate sensorless rotor position estimation. By comparing with rotor positon estimations without the proposed compensation and HF carrier current based method, the effectiveness of improved sensorless rotor position estimation has been demonstrated experimentally, as well as the application to dual 3-phase SFPM machines

Paxillin facilitates timely neurite initiation on soft-substrate environments by interacting with the endocytic machinery.

Neurite initiation is the first step in neuronal development and occurs spontaneously in soft tissue environments. Although the mechanisms regulating the morphology of migratory cells on rigid substrates in cell culture are widely known, how soft environments modulate neurite initiation remains elusive. Using hydrogel cultures, pharmacologic inhibition, and genetic approaches, we reveal that paxillin-linked endocytosis and adhesion are components of a bistable switch controlling neurite initiation in a substrate modulus-dependent manner. On soft substrates, most paxillin binds to endocytic factors and facilitates vesicle invagination, elevating neuritogenic Rac1 activity and expression of genes encoding the endocytic machinery. By contrast, on rigid substrates, cells develop extensive adhesions, increase RhoA activity and sequester paxillin from the endocytic machinery, thereby delaying neurite initiation. Our results highlight paxillin as a core molecule in substrate modulus-controlled morphogenesis and define a mechanism whereby neuronal cells respond to environments exhibiting varying mechanical properties