116 research outputs found
A novel electromagnetic energy harvester based on the bending of the sole
No full textConverting mechanical energy into electrical energy during human walking can power the portable electronic devices applied in navigation, gait monitoring, and biofeedback, etc. This paper presents a novel electromagnetic energy harvester based on the bending of the sole to provide electric energy to portable sensors and small devices. The harvester mainly consists of a four-bar linkage, a one-way clutch, a propeller shaft, two bevel gears, a gearbox, and a brushless DC electromagnetic generator, which can covert the bending motion of the sole into the unidirectional rotation of the generator shaft. Then the generator will rotate and generate electrical energy (DC). A prototype is fabricated to demonstrate the feasibility and the practical application of the harvester, and the working principle is explained. The output voltage and output power at different walking speeds are acquired and analyzed. Numerical and experimental results demonstrate that the presented harvester works well and has considerable output power at human normal walking speeds. For a 72 kg test person, the presented harvester can effectively work at the walking speeds ranging from 1 km/h to 7 km/h with the average output power around 10 mW, which is high enough to power low-powered portable devices. The average power density is about 0.43 mW/cm
3, 0.42 mW/cm
3 and 0.2 mW/cm
3 at the walking speed of 4 km/h, 6 km/h and 8 km/h, respectively. Overall, this research may provide a new way and framework to design high-efficiency energy harvesters used for human motion energy harvesting.
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Optimized design of self-powered SSHI interface circuit for enhanced vibration energy harvesting
No full textVibrational energy in ambient environment can be transformed into electrical power through piezoelectric energy harvesters, and using synchronized switch harvesting on inductor (SSHI) techniques can significantly improve energy extraction efficiency. To enhance energy harvesting efficiency, this study proposes an efficient self-powered parallel SSHI (ESP-PSSHI) interface circuit. It enhances the passive peak detection switch, simplifies the circuit topology, reduces switching delay, and minimizes the "second inversion", contributing to increased energy harvesting efficiency. To improve the impedance-matching characteristics of the circuit, the proposed circuit is combined with a DC-DC converter module and finally, a stable electrical output is achieved. The performance of the ESP-PSSHI circuit in power generation is analyzed through simulation and subsequently verified via experimentation. Experiments show that the maximum output power of the ESP-PSSHI circuit is 2.42 and 1.16 times higher than the output power of the standard energy harvesting (SEH) circuit and self-powered parallel SSHI (SP-PSSHI) circuit, respectively. Through capacitor charging experiments, it is concluded that the output power of the optimized ESP-PSSHI circuit is 1.5 times the output power of the LTC3588-1 circuit
Multistability phenomenon in signal processing, energy harvesting, composite structures, and metamaterials: A review
No full textMultistability is the phenomenon of multiple coexistent stable states, which are highly sensitive to perturbations, initial conditions, system parameters, etc. Multistability has been widely found in various scientific areas including biology, physics, chemistry, climatology, sociology, and ecology. In a number of systems where multistability naturally exists, it is found to be undesirable because of the involuntary interwell or chaotic switching among dynamical states that disorder the systems and cause instability. However, in recent decades, researchers have identified numerous benefits of multistability and have devoted research efforts to artificially creating it for a wide range of applications, including signal processing, energy harvesting, composite structures and metamaterials, and micro-/nano-electromechanical actuators. This is because of the unique characteristics of multistability, such as rich potential structure, interwell dynamics, broadband nature, and alleviation of the input energy to sustain stable states, which may play different advantageous roles depending on their applications. In this review, we introduce how researchers create the key of multistability and utilize it to open a new world of theories, materials, and structures. We concentrate on developing histories from bistability to multistability in several potential applications. Different designs of digital and physical multistable systems, and their modeling, performance quantifiers, advantageous mechanisms, and improved techniques are reviewed and discussed in depth. Furthermore, we summarize the key issues and challenges of application-oriented multistability and the corresponding possible solutions, from the phenomenon itself to its realistic implementation. Finally, we provide the prospects for future studies on multistability in more developing research fields
Stochastic and deterministic responses of an asymmetric quad-stable energy harvester
No full textIn this paper, stochastic and deterministic dynamical properties of an asymmetric quad-stable energy harvester are explored for improving the energy harvesting performance. Firstly, the harmonic balance method is utilized to explicitly derive the coupled relationship of the displacement amplitude, the constant term, and the output voltage amplitude. By means of direct numerical results, the existence of the multi-valued phenomenon of the asymmetric quad-stable energy harvester is found. Especially, the constant term is asymmetric due to the asymmetric characteristics. In addition, the influence of the depth of different potential wells on the highest orbit of inter-well oscillations is discussed. Finally, it is found that the symbol change of the largest Lyapunov exponent (LLE) of the harvester is consistent with the results derived by bifurcation diagrams, which verify the effectiveness of the LLE. The existence of noise can induce the harvester to transform from period motions to chaotic motions. The transition of the probability density function (PDF) of the harvester is influenced by the potential distribution and depth
Interactive research on children's entertainment facilities in Shanghai newly-built residential communities
Full text linkLAUREA MAGISTRALELo sviluppo dell'urbanizzazione in Cina non solo ha portato allo sviluppo fiorente di nuove comunità, ma ha anche arricchito le condizioni materiali, la vita sociale e le varie attività, che ha imposto requisiti più elevati all'ambiente di intrattenimento a misura di bambino nella loro crescita. Come parte essenziale delle attività per bambini, le strutture e gli spazi di intrattenimento arricchiscono direttamente o indirettamente la vita di svago, in particolare per i bambini in crescita, che è la fase più importante e sensibile della loro vita. Tuttavia, lo sviluppo dello spazio di intrattenimento per bambini e delle strutture nelle comunità di nuova costruzione è ancora molto lento, privo di funzioni di più tipi, di divertimenti e di interazioni con altri che potrebbero lasciare i bambini lontani dalle esigenze psicologiche e fisiche e non fornire ai bambini con un'infanzia positiva e felice in modo che possa influire sullo sviluppo della salute fisica e mentale dei bambini.
A tal fine, prendere come esempio Shanghai, l'obiettivo della ricerca del progetto è di analizzare le strutture di intrattenimento per bambini e lo spazio nelle comunità residenziali di nuova costruzione, per esplorare i punti chiave della progettazione di strutture e spazi di intrattenimento interattivo per bambini attraverso la crescita di i bambini, lo sviluppo, il comportamento, le caratteristiche psicologiche, e di combinare con lo stato di sviluppo del design nazionale e internazionale e l'analisi di eccellenti casi di progettazione per capire le lacune e scoprire le soluzioni ai problemi basati sulla teoria dello sviluppo cognitivo, psicologia comportamentale e ricerca teorica interattiva Nel frattempo, attraverso la ricerca sul campo e l'analisi del comportamento interattivo delle strutture di intrattenimento per bambini e dello spazio nelle nuove aree residenziali di Shanghai, sono riassunti gli elementi chiave e le caratteristiche del design interattivo delle strutture di intrattenimento per bambini, fornendo così nuove idee e metodi per migliorare le strutture di intrattenimento per bambini e anche la costruzione di un quadro teorico iniziale di base e di un design pratico nel giardino di Tianan per strutture e spazi interattivi per l'intrattenimento dei bambini.The development of urbanization in China not only led to the flourishing development of new communities, but also enriched material conditions, social life, and the various activities, which has imposed higher requirements on child-friendly entertainment environment in their growth. As an essential part of children activities, the entertainment facilities and spacesdirectly or indirectly enrich leisure life, especially for the growing children, which is the most important and sensitive stage in their life. However, the development of children's entertainment space and facilities in newly-built communities is still very slow, lacking in multi-types functions, funs and interactions with others that could be leave children out of consideration of psychological and physical needs and fails to provide children with a positive, happy childhood so that may affect physical and mental health development of children.
To this end, take Shanghai as an example, the research goal of the project is aim to analyze the children's entertainment facilities and space in newly-built residential communities, to explore the key points of designing children’s interactive entertainment facilities and space through the growth of children, development, behavior, psychological characteristics, and to combine with the development status of domestic and international design as well as analysis of excellent designing cases to understand the gaps and find out the solutions to the problems based on cognitive development theory, behavioral psychology and interactive theoretical research. Meanwhile, through the field research and interactive behavior analysis of children's entertainment facilities and space in new residential areas in Shanghai, the key elements and characteristics of the interactive design of children's entertainment facilities are summarized, thus providing new ideas and methods for improving children's entertainment facilities and also building initially basic theoretical framework as well as practical design in Tianan Garden for interactive children’s entertainment facilities and spaces
Service design research of the creative park with the theme of ICH. Taking Shanghai Shangzhifang creative park as an example
Full text linkLAUREA MAGISTRALEL'eredità di ICH ha una lunga strada da percorrere. Ci sono molte difficoltà e sfide di fronte all'ICH. Le industrie culturali e creative sono diventate la forza trainante per lo sviluppo economico della Cina. I parchi creativi sono diventati i principali vettori e metodi per l'accumulo di industrie culturali e creative. La cultura ICH è caratterizzata dalla sua ricchezza e diversità e offre nuove opportunità per l'ereditarietà dell'ICH che richiede lo sviluppo di una cultura della sordità. Pertanto, l'attracco scientifico tra la cultura ICH e il parco creativo ha un grande valore pratico nell'eredità della cultura non-heritage. In questo articolo, l'autore ha studiato i principi e i metodi rilevanti della progettazione del servizio, portando il parco creativo di Shanghai Shangzhifang come un esempio per costruire un sistema di servizi di parchi creativi non creativi. Connetti l'esperienza e le sensazioni dell'utente nel processo di front-end del parco creativo non creativo con il modello di business e il flusso di servizi del parco creativo back-end. In questo articolo, l'autore combina organicamente modelli di progettazione del servizio con modelli di business, quindi esplora gli schemi concreti e la profondità della fattibilità della connessione tra parchi creativi e culture ereditarie.
In primo luogo, nella ricerca l'autore ha introdotto il principio di progettazione e la metodologia del design del servizio e ha sintetizzato e sintetizzato la situazione attuale dell'aumento e dello sviluppo delle culture di eredità e dei parchi creativi. Allo stesso tempo, combina casi studio rilevanti di ICH. La funzione, il metodo di generazione e le parti interessate del concetto di parco creativo ICH sono stati pettinati e le idee di progettazione del servizio e il contenuto del parco creativo non storico sono stati elaborati in dettaglio. In secondo luogo, attraverso la ricerca sullo status quo dello Shangzhifang Creative Park, l'autore ha scoperto il contatto di servizio di Shangzhifang per sviluppare il parco creativo ICH.
In secondo luogo, l'autore investiga sulla situazione attuale del parco creativo di Shangzhifang e scopre i punti di contatto del servizio dello sviluppo di ICH Park di Shangzhifang. Attraverso la classificazione degli utenti, sono stati condotti questionari e interviste approfondite sugli eredi e turisti dell'ICH. Con l'aiuto della classificazione del gruppo target dell'utente, l'autore ha suddiviso i file utente dello Shangzhifang Creative Park in tre categorie: appassionati di cultura, interazione familiare e impiegati ordinari. Questi tre file coprono fondamentalmente le esigenze e le tendenze stilistiche degli utenti del parco creativo di ICH che potrebbero essere coinvolti.
Nell'applicazione di progettazione del servizio del parco creativo di Shangzhifang, questo articolo applicava il processo standard del concetto di servizio, visione e scenario del servizio, analizzando il soggetto interessato, la mappa dell'offerta di servizi, la mappa del sistema di servizio, il piano di servizio e lo storyboard per stabilire la piattaforma di servizi, lo spazio, il marchio e la pianificazione degli eventi di Shangzhifang e mostra i risultati finali del progetto di servizio. Allo stesso tempo, è stata proposta anche una strategia di esperienza utente multi-livello per il campus: esperienza sensoriale, esperienza narrativa, esperienza immersiva, esperienza di co-creazione ed esperienza di pensiero. La trasmissione efficace di ICH è lo scopo. I parchi creativi sono i media. Il service design è un mezzo e un nuovo motore per l'ereditarietà e l'innovazione di ICH.The inheritance of ICH has a long way to go. There are many difficulties and challenges facing the ICH. Cultural and creative industries have become the supporting force for China's economic development. Creative parks have become the main carriers and methods for the accumulation of cultural and creative industries. The ICH culture is characterized by its richness and diversity, and it brings new opportunities for the inheritance of the ICH requires the development of a culture of deafness. Therefore, the scientific docking between the ICH culture and the creative park has great practical value in the inheritance of non-heritage culture. In this paper, the author studied the relevant principles and methods of service design, taking Shanghai Shangzhifang creative park as an example to build a non-creative creative park service system. Connect the user's experience and feelings in the front-end process of the non-creative creative park with the business model and service flow of the back-end creative park. In this article, the author organically combines service design patterns with business models then explore the concrete schemes and depth of the feasibility of the connection between creative parks and inheritance cultures.
Firstly, in the research the author introduced the design principle and methodology of service design and combed and summarized the current situation of the rise and development of the inheritance cultures and creative parks. At the same time, it combines relevant case studies of ICH. The function, generation method and stakeholders of the concept of ICH creative park were combed, and the service design ideas and content of the non-heritage creative park were elaborated in detail. Secondly, through the research on the status quo of Shangzhifang Creative Park, the author have found out the service contact of Shangzhifang to develop the ICH creative park.
Secondly, the author investigate the current situation of the creative park of Shangzhifang and find out the service touchpoints of Shangzhifang’s development of ICH Park. Through user classification, questionnaires and in-depth interviews were conducted on the ICH inheritors and tourists. With the help of the classification of the user's target group, the author divided the user files of the Shangzhifang Creative Park into three categories: cultural enthusiasts, family interaction, and ordinary office workers. These three files basically cover the needs and style tendencies of ICH creative park users that may be involved.
In the service design application of the Shangzhifang creative park, this article applied the standard process of service design’s concept, vision and scenario of the service, analyzing the relevant stakeholder, service offering map, service system map, service blueprint and storyboard in order to establish the Shangzhifang’s service platform, space, brand and event planning, and showing the final service design results. At the same time, a multi-level user experience strategy for the campus was also proposed: sensory experience, storytelling experience, immersive experience, co-creation experience and thinking experience. The effective transmission of ICH is the purpose. Creative parks are the media. Service design is a means and a new engine for inheritance and innovation of ICH
Author reported blinding credibility testing.
No full text<p>Author reported blinding credibility testing.</p
Light-matter interactions of two-dimensional materials and the coupled nanostructures
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 207-244).Two-dimensional (2D) materials have gained increasing attention due to their unique and extraordinary electrical and optoelectronic properties. These properties can be largely attributed to the fundamental light-matter interactions. This thesis project uses spectroscopy techniques and focuses on the study of the light-matter interaction in 2D materials, as well as their coupling with other nanostructures, which are essential in achieving useful optoeletronic applications with 2D materials. First, the fundamental properties of 2D materials were investigated using spectroscopy. Photoluminescence (PL) spectroscopies of MoS₂ and its related structures were studied, showing that the interaction between MoS2 layers and other dielectrics can strongly affect their PL emissions, exciton and trion properties. Moreover, combining Raman spectroscopy and X-ray photoelectron spectroscopy, the effects of substrates and defects for MoS₂ have been revealed. Next, interlayer vibrational properties of 2D materials are studied utilizing low-frequency Raman spectroscopy. Twisted bilayer MoS2 and few-layer black phosphorus were chosen to demonstrate the interlayer coupling from the perspective of interlayer breathing and shear Raman modes. These exemplary studies offer a great tool to investigate the interlayer coupling, thickness, and stacking configurations of 2D materials using low-frequency Raman spectroscopy. The anisotropic light-matter interactions of 2D materials were also examined. Using polarization dependent Raman and optical absorption spectroscopies, together with first-principles density functional theory analysis and group theory, the anisotropy of electron-photon and electron-phonon interactions can be revealed. This method can experimentally exhibit the anisotropy of electron-phonon interactions in 2D materials, and can be generalized to other layered materials with in-plane anisotropy. The interactions of 2D materials with other materials systems were also investigated using optical spectroscopies. The interactions of 2D materials and selected organic molecules were revealed using graphene-enhanced Raman spectroscopy. The interaction between 2D materials and plasmonic nanocavities were found to exhibit an interesting enhancement phenomenon for the optical response of 2D materials. Overall, the studies presented in this thesis work show broad opportunities for using spectroscopic tools to study light-matter interactions of 2D materials, as well as the combined system of 2D materials and other nanostructures. This work is significant fundamentally, and also offers useful guidelines for practical applications of 2D materials in electronics and optoelectronics.by Shengxi Huang.Ph. D
Transient and Harmonic Unipolar Hysteresis Model of Piezoelectric Actuators Using a System-Level Approach
No full textThanks to their integrability and good electromechanical conversion abilities, piezoelectric actuators are a good choice for many actuation applications. However, these elements feature a frequency-dependent hysteresis response that may yield complex control implementation. The purpose of this paper is to provide the extension of a simple hysteresis model based on a system-level approach linking the strain derivative to the driving voltage derivative and taking into account the dynamic behavior of the hysteretic response of the actuator. The proposed enhancement consists of transient and harmonic regimes, allowing to extend the quasi-static model to dynamic behavior with any frequency. In particular, initial strain shift arising from stabilization and accommodation effects as well as frequency-dependent hysteresis shape are considered. The inclusion of the system dynamics in the model is obtained thanks to fractional derivatives and associated fractional transfer functions, allowing the consideration of the full actuator history as well as a fine tuning of the system dynamics over a wide frequency band. Finally, a numerical example of linearized control through compensation loop is provided, demonstrating the interest in the proposed approach for providing a computationally-efficient, simple yet efficient way for finely predicting the actuator response and thus designing appropriate controllers
High-Performance Piezoelectric Energy Harvesters and Their Applications
No full textEnergy harvesting holds great potential to achieve long-lifespan self-powered operations of wireless sensor networks, wearable devices, and medical implants, and thus has attracted substantial interest from both academia and industry. This paper presents a comprehensive review of piezoelectric energy-harvesting techniques developed in the last decade. The piezoelectric effect has been widely adopted to convert mechanical energy to electricity, due to its high energy conversion efficiency, ease of implementation, and miniaturization. From the viewpoint of applications, we are most concerned about whether an energy harvester can generate sufficient power under a variable excitation. Therefore, here we concentrate on methodologies leading to high power output and broad operational bandwidth. Different designs, nonlinear methods, optimization techniques, and harvesting materials are reviewed and discussed in depth. Furthermore, we identify four promising applications: shoes, pacemakers, tire pressure monitoring systems, and bridge and building monitoring. We review new high-performance energy harvesters proposed for each application. With the rapid advances in wireless sensors, implantable electronics, and wearable devices, the demand for high-power-density and long-lifespan power sources is becoming increasingly stronger. Energy harvesting, emerging as an alternative energy solution to batteries, holds great potential to achieve self-powered autonomous operations of such low-power electronic devices, and thus has recently attracted much attention from both academia and industry. The piezoelectric effect is widely adopted to convert mechanical energy to electrical energy, due to its high energy conversion efficiency, ease of implementation, and miniaturization. This paper presents a comprehensive and critical review of state-of-the-art research on piezoelectric energy harvesting. From the viewpoint of applications, we are most concerned about whether an energy harvester can generate sufficient power under variable excitation. Therefore, here we concentrate on methodologies leading to high power output and broad operational bandwidth. A variety of designs, nonlinear methods, optimization techniques, and harvesting materials are reviewed and discussed in depth. The study also evaluates different figures of merit and presents a systematic performance comparison on recently proposed energy harvesters. Furthermore, we identify four promising applications: shoes, artificial pacemakers, tire pressure monitoring systems, and bridge and building monitoring. The excitation characteristics of each application are analyzed and corresponding harvesting methods discussed. The piezoelectric energy-harvesting technology has experienced significant progress in the past 10 years. However, research on energy harvesters is mostly conducted without specific applications, and reliability and system integration have not been well examined. More research is expected to deal with these issues to facilitate in turning decades of research efforts on energy harvesting into tangible benefits in our daily life. Energy harvesting, emerging as an alternative energy solution to batteries, holds great potential to achieve self-powered autonomous operations of low-power electronic devices, such as wireless sensors, implantable electronics, and wearable devices. This paper presents a comprehensive review of state-of-the-art piezoelectric energy-harvesting techniques that lead to high power output and broad operational bandwidth. In-depth discussions are conducted on promising applications, including shoes, artificial pacemakers, tire pressure monitoring systems, and bridge and building health monitoring.</p
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