Integration of an Active Filter and a Single-Phase AC/DC Converter with Reduced Capacitance Requirement and Component Count

Existing methods of incorporating an active filter into an AC/DC converter for eliminating electrolytic capacitors usually require extra power switches. This inevitably leads to an increased system cost and degraded energy efficiency. In this paper, a concept of active-filter integration for single-phase AC/DC converters is reported. The resultant converters can provide simultaneous functions of power factor correction, DC voltage regulation, and active power decoupling for mitigating the low-frequency DC voltage ripple, without an electrolytic capacitor and extra power switch. To complement the operation, two closed-loop voltage-ripple-based reference generation methods are developed for controlling the energy storage components to achieve active power decoupling. Both simulation and experiment have confirmed the eligibility of the proposed concept and control methods in a 210-W rectification system comprising an H-bridge converter with a half-bridge active filter. Interestingly, the end converters (Type I and Type II) can be readily available using a conventional H-bridge converter with minor hardware modification. A stable DC output with merely 1.1% ripple is realized with two 50-μF film capacitors. For the same ripple performance, a 900-μF capacitor is required in conventional converters without an active filter. Moreover, it is found out that the active-filter integration concept might even improve the efficiency performance of the end converters as compared with the original AC/DC converter without integration

A plug-and-play ripple mitigation approach for DC-links in hybrid systems

© 2016 IEEE.In this paper, a plug-and-play ripple mitigation technique is proposed. It requires only the sensing of the DC-link voltage and can operate fully independently to remove the low-frequency voltage ripple. The proposed technique is nonintrusive to the existing hardware and enables hot-swap operation without disrupting the normal functionality of the existing power system. It is user-friendly, modular and suitable for plug-and-play operation. The experimental results demonstrate the effectiveness of the ripple-mitigation capability of the proposed device. The DC-link voltage ripple in a 110 W miniature hybrid system comprising an AC/DC converter and two resistive loads is shown to be significantly reduced from 61 V to only 3.3 V. Moreover, it is shown that with the proposed device, the system reliability has been improved by alleviating the components' thermal stresses

A multi-task learning CNN for image steganalysis

Convolutional neural network (CNN) based image steganalysis are increasingly popular because of their superiority in accuracy. The most straightforward way to employ CNN for image steganalysis is to learn a CNN-based classifier to distinguish whether secret messages have been embedded into an image. However, it is difficult to learn such a classifier because of the weak stego signals and the limited useful information. To address this issue, in this paper, a multi-task learning CNN is proposed. In addition to the typical use of CNN, learning a CNN-based classifier for the whole image, our multi-task CNN is learned with an auxiliary task of the pixel binary classification, estimating whether each pixel in an image has been modified due to steganography. To the best of our knowledge, we are the first to employ CNN to perform the pixel-level classification of such type. Experimental results have justified the effectiveness and efficiency of the proposed multi-task learning CNN

Direct AC/DC Rectifier With Mitigated Low-Frequency Ripple Through Inductor-Current Waveform Control

In a rectification system with unity power factor, the input power consists of a dc and a double-line frequency power component. Traditionally, an electrolytic capacitor (E-Cap) is used to buffer the double-line frequency power such that the dc output presents a small voltage ripple. The use of E-Cap significantly limits the lifetime of the rectifier system. In this paper, a differential ac/dc rectifier based on the use of an inductor-current waveform control methodology is proposed such that a single-stage direct ac/dc rectification without the need of an E-Cap for buffering the double-line frequency power, and a front-stage diode rectifier circuit can be achieved. The feasibility of the proposal has been practically confirmed in an experimental prototype.published_or_final_versio

Direct AC/DC rectifier with mitigated low-frequency ripple through waveform control

In a rectification system with unity power factor, the input power consists of a DC and a double-line frequency power component. Traditionally, an electrolytic capacitor (E-Cap) is used to buffer the double-line frequency power such that the DC output presents a small voltage ripple. The use of E-Cap significantly limits the lifetime of the rectifier system. In this paper, a differential AC/DC rectifier based on the use of an inductor-current waveform control methodology is proposed. The proposed configuration achieves single-stage direct AC/DC rectification without the needs of a front-stage diode rectifier circuit, an input EMI filter, and an E-Cap for buffering the double-line frequency power. The feasibility of the proposal has been practically confirmed in an experimental prototype. © IEEE.published_or_final_versio

Power Flow Analysis and Critical Design Issues of Retrofit Light-Emitting Diode (LED) Light Bulb

published_or_final_versio

A Survey of Embodied AI: From Simulators to Research Tasks

There has been an emerging paradigm shift from the era of "internet AI" to "embodied AI", where AI algorithms and agents no longer learn from datasets of images, videos or text curated primarily from the internet. Instead, they learn through interactions with their environments from an egocentric perception similar to humans. Consequently, there has been substantial growth in the demand for embodied AI simulators to support various embodied AI research tasks. This growing interest in embodied AI is beneficial to the greater pursuit of Artificial General Intelligence (AGI), but there has not been a contemporary and comprehensive survey of this field. This paper aims to provide an encyclopedic survey for the field of embodied AI, from its simulators to its research. By evaluating nine current embodied AI simulators with our proposed seven features, this paper aims to understand the simulators in their provision for use in embodied AI research and their limitations. Lastly, this paper surveys the three main research tasks in embodied AI -- visual exploration, visual navigation and embodied question answering (QA), covering the state-of-the-art approaches, evaluation metrics and datasets. Finally, with the new insights revealed through surveying the field, the paper will provide suggestions for simulator-for-task selections and recommendations for the future directions of the field.Comment: Under Review for IEEE TETC

Effects of the Physical Microenvironment on Endometrial Cancer Cells (Ishikawa)

With the realization that mechanical signals are important in controlling cancer cell behaviours, a new in vitro model has been developed to incorporate physical signals in laboratory studies. Here, we developed a system to fabricate hard polymers with imprinted cell topography, which we called a Bioimprint, and then we used the Bioimprint as the platform to culture endometrial cancer cells on. With Bioimprint high resolution of cell replicas were produced with cell-like features that retain all the micro- and nanoscale details of the cells. This enabled us, importantly, to study the effect of surface physical topography on endometrial cancer cell behaviours. The physical topography we used here was the cell-like topography that the cells encounter in real cell microenvironments. We fabricated the Bioimprint of cells onto polymethacrylate (pMA) and compared the cells cultured on it to the cells on flat pMA. pMA is not a common cell culture material, therefore, we compared cell culture on pMA with the conventional cell culture materials: glass and polystyrene (pST). We then fabricated the Bioimprint onto pST, and compared the response of cells cultured on the replica with that cultured on the flat pST. Moreover, on pST, the Bioimprint was made in two forms: pit-like (negative) versus hump-like (positive) topographies, which enabled us to further investigate the effect of distinct topographies on cell behaviours. We also extended our study on flat and pST Bioimprints to study the effect of culture serum, fetal bovine serum (FBS), on cell responses to surface physical topography. In this report, we characterized the behaviours of endometrial cancer cells and studied the biological changes in response to culture substrate materials and culture substrate with cell-like topography. We examined cell adhesion, morphology, spreading, expression of adhesion molecules and growth. The studies of pST Bioimprints were extended to examine the cell protein profile, and cell responses to anticancer agents, in serum-supplemented or serum-free culture media. The comparison between glass, tissue culture grade pST and pMA showed that substrate material modulated cell behaviours. Additionally, imprinting with cell-like topography also altered cell behaviours. Here, we showed that Ishikawa endometrial cancer cells spread wider and grew faster on glass and pST compared to pMA. Further, on the pMA surface that was imprinted with cell-like topography, the cells spread and grew better compared to cells on flat pMA. On the other hand, when pST, which is a favourable cell culture surface, was imprinted with the cell-like topography, the topographical effect was to restrict cell spreading and growth. Most importantly, the change in cell growth behaviour was modulated through different proliferation biomolecules on each of these pMA and pST Bioimprints, indicating again the interaction of chemical and physical topography in regulating cell behaviours. In addition, the comparison between pST hump-like versus the pit-like topographies showed that the cells on the hump-like topography showed a greater response of an alteration of cell growth, expression of adhesion molecules when compared to cells on flat substrate. Furthermore, relative to cells on (f)pST proteomics analysis similarly showed that cells on hump-like topography had more alteration in protein expression than cells on pit-like topography. Most of these identified proteins were involved in cell energy homeostasis, growth and structural modulation. Additionally, the extended studies with culture serum without FBS again showed that endometrial cancer cells responded to physical topography. The cell responses were different from those in culture medium supplemented with FBS. This again indicated that the topographical influences on cells were in turn affected by chemical factors (the biological source of serum chemical factors). Notably, cell culture in serum free medium similarly showed a greater tropographical response to the hump-like topography compared to cells on a flat substrate. Here, we reveal the potential of targeting cell mechano-signalling as cancer treatment, and also this project describes a culture platform that inherently incorporates physical signals in laboratory cell culture studies. This is the first report that showed that Ishikawa endometrial cancer cells respond to the culture substrate material and cell-like physical topography