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1.
Opt Express ; 27(24): 35448-35467, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31878716

RESUMO

We demonstrate a highly sensitive, low-cost, environmental-friendly pressure sensor derived from a wool-based pressure sensor with wide pressure sensing range using wool bricks embedded with a Ag nano-wires. The easy fabrication and light weight allow portable and wearable device applications. Wth the integration of a light-emitting diode possessing multi-wavelength emission, we illustrate a hybrid multi-functional LED-integrated pressure sensor that is able to convert different applied pressures to light emission with different wavelengths. Due to the high sensitivity of the pressure sensor, the demonstration of acoustic signal detection has also been presented using sound of a metronome and a speaker playing a song. This multi-functional pressure sensor can be implemented to technologies such as smart lighting, health care, visible light communication (VLC), and other internet of things (IoT) applications.

2.
Opt Express ; 27(24): 35700-35709, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31878737

RESUMO

This paper proposes a distributed collaborative learning approach for cognitive and autonomous multi-domain elastic optical networking (EON). The proposed approach exploits a knowledge-defined networking framework which leverages a broker plane to coordinate the operations of multiple EON domains and applies machine learning (ML) to support autonomous and cognitive inter-domain service provisioning. By employing multiple distributed ML blocks learning domain-level features and working with broker plane aggregation ML blocks (through the chain rule-based training), the proposed approach enables to develop cognitive networking applications that can fully exploit the multi-domain EON states while obviating the need for the raw and confidential intra-domain data. In particular, we investigate end-to-end quality-of-transmission estimation application using the distributed learning approach and propose three estimator designs incorporating the concepts of multi-task learning (MTL) and transfer learning (TL). Evaluations with experimental data demonstrate that the proposed designs can achieve estimation accuracies very close to (with differences less than 0.5%) or even higher than (with MTL/TL) those of the baseline models assuming full domain visibility.

3.
J Healthc Eng ; 2018: 2723178, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30002803

RESUMO

Fast walking is a common exercise for most people to promote health. However, a higher cadence due to fast walking on ordinary or uneven ground raises the risk of tripping. To investigate the tripping issue, research to observe the gait in fast walking is needed. To explore the relationship between fast gait and the risk of tripping, a gait recording system with a specific synchronization mechanism was developed in this work. The system can acquire gait signals from wearable sensors and action cameras at different cadences. Meanwhile, algorithms for gait cycle segmentation and characteristic extraction were proposed for analyzing a fast gait. In the gait analysis, the correlations of low, moderate, and high cadence in cueing and no cueing gaits were computed, and two results were obtained. First, the higher the cadence is, the larger the motion strength in the terminal foot swing will be and the smaller the motion strength at the starting foot swing. Second, the decreased distance of foot clearance becomes more conspicuous as the cadence increased, especially if one is walking more than 120 beats. The results indicate that fast walking with bigger strides and lower cadence is the best way to maintain safety in moving over ordinary ground.


Assuntos
Acidentes por Quedas , Análise da Marcha/métodos , Processamento de Sinais Assistido por Computador , Caminhada/fisiologia , Algoritmos , Pé/fisiologia , Humanos , Gravação em Vídeo
4.
Nano Lett ; 17(10): 6228-6234, 2017 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-28926272

RESUMO

We demonstrated a monolithic GaN-InGaN core-shell nanorod lattice lasing under room temperature. The threshold pumping density was as low as 140 kW/cm2 with a quality factor as high as 1940. The narrow mode spacing between lasing peaks suggested a strong coupling between adjacent whisper gallery modes (WGM), which was confirmed with the far-field patterns. Excitation area dependent photoluminescence revealed that the long-wavelength lasing modes dominated the collective lasing behavior under a large excitation area. The excitation-area-dependent lasing behavior resulted from the prominent optical coupling among rods. According to the optical mode simulations and truncated-rod experiments, we confirmed that the fine-splitting of lasing peaks originated from the coupled supermodes existing in the periodic nanorod lattices. With wavelength-tunable active materials and a wafer-level scalable processing, patterning optically coupled GaN-InGaN core-shell nanorods is a highly practical approach for building various on-chip optical components including emitters and coupled resonator waveguides in visible and ultraviolet spectral range.

5.
Opt Express ; 24(17): 19978-87, 2016 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-27557273

RESUMO

A large enhancement of color-conversion efficiency of colloidal quantum dots in light-emitting diodes (LEDs) with novel structures of nanorods embedded in microholes has been demonstrated. Via the integration of nano-imprint and photolithography technologies, nanorods structures can be fabricated at specific locations, generating functional nanostructured LEDs for high-efficiency performance. With the novel structured LED, the color-conversion efficiency of the existing quantum dots can be enhanced by up to 32.4%. The underlying mechanisms can be attributed to the enhanced light extraction and non-radiative energy transfer, characterized by conducting a series of electroluminescence and time-resolved photoluminescence measurements. This hybrid nanostructured device therefore exhibits a great potential for the application of multi-color lighting sources.

6.
Nanoscale ; 8(2): 1192-9, 2016 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-26666367

RESUMO

Green LEDs do not show the same level of performance as their blue and red cousins, greatly hindering the solid-state lighting development, which is the so-called "green gap". In this work, nano-void photonic crystals (NVPCs) were fabricated to embed within the GaN/InGaN green LEDs by using epitaxial lateral overgrowth (ELO) and nano-sphere lithography techniques. The NVPCs act as an efficient scattering back-reflector to outcouple the guided and downward photons, which not only boost the light extraction efficiency of LEDs with an enhancement of 78% but also collimate the view angle of LEDs from 131.5° to 114.0°. This could be because of the highly scattering nature of NVPCs which reduce the interference giving rise to Fabry-Perot resonance. Moreover, due to the threading dislocation suppression and strain relief by the NVPCs, the internal quantum efficiency was increased by 25% and droop behavior was reduced from 37.4% to 25.9%. The enhancement of light output power can be achieved as high as 151% at a driving current of 350 mA. Giant light output enhancement and directional control via NVPCs point the way towards a promising avenue of solid-state lighting.

7.
Materials (Basel) ; 8(3): 1204-1212, 2015 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-28787997

RESUMO

This work describes a novel architecture to realize high-performance gallium nitride (GaN) bulk acoustic wave (BAW) resonators. The method is based on the growth of a thick GaN layer on a metal electrode grid. The fabrication process starts with the growth of a thin GaN buffer layer on a Si (111) substrate. The GaN buffer layer is patterned and trenches are made and refilled with sputtered tungsten (W)/silicon dioxide (SiO2) forming passivated metal electrode grids. GaN is then regrown, nucleating from the exposed GaN seed layer and coalescing to form a thick GaN device layer. A metal electrode can be deposited and patterned on top of the GaN layer. This method enables vertical piezoelectric actuation of the GaN layer using its largest piezoelectric coefficient (d33) for thickness-mode resonance. Having a bottom electrode also results in a higher coupling coefficient, useful for the implementation of acoustic filters. Growth of GaN on Si enables releasing the device from the frontside using isotropic xenon difluoride (XeF2) etch and therefore eliminating the need for backside lithography and etching.

8.
Chem Asian J ; 9(6): 1601-10, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24771487

RESUMO

A new series of model dye molecules composed of three multibranched analogues based on the tetrasubstituted tetraethynylethylene structural motif have been synthesized and experimentally shown to possess strong and widely dispersed two-photon absorption (2PA) in the near-IR region. It was found that the spectral position of the major 2PA band could be tuned by the electronic nature of the selected substitution units. The studied model fluorophores also exhibited fairly low photodegradation of their fluorescence intensity even under prolonged UV-light irradiation, which is beneficial for the development of fluorescence probes that are needed for long-term light exposure. Furthermore, representative chromophores were selected to demonstrate the power-control properties within the femtosecond and nanosecond time domains.


Assuntos
Enedi-Inos/química , Corantes Fluorescentes/química , Corantes Fluorescentes/síntese química , Fótons , Absorção Fisico-Química , Estrutura Molecular , Piridazinas/química , Piridinas/química , Quinoxalinas/química , Espectrometria de Fluorescência
9.
Opt Express ; 22(4): 4516-22, 2014 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-24663772

RESUMO

Micro-patterned PDMS film was fabricated and combined with LED chip on board (COB) package to improve the emission uniformity of LED chip. The micro scale patterned sapphire substrate (PSS) was used as a mold to fabricate micro-cone patterned PDMS (MC-PDMS) film. A strong scattering effect from this MC-PDMS film can be verified by the high haze ratio and the Bi-directional Transmission effect. The angle dependent color temperature measurement system was used to measure the ΔCCT of COB with and without MC-PDMS. The measurement results indicate that the ΔCCT was reduced from 1025K to 428K. This improvement can effectively eliminate the yellow ring effect of LED chip. This technology can be thus considered as a cost-effective way for the next generation of light source packages.

10.
Chem Asian J ; 8(9): 2102-10, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23744812

RESUMO

Two analogous multipolar chromophores (1 and 2) that contained 2,3,8-trisubstituted indenoquinoxaline moieties have been synthesized and characterized for their two-photon absorption properties, both in the femtosecond and nanosecond time regimes. We demonstrated that their multi-branched framework structures, which incorporated appropriately functionalized indenoquinoxaline units, afforded large molecular nonlinear absorptivities within the studied spectroscopic range. Effective optical-power-limiting and stabilization behaviors in the nanosecond regime of dye molecule (2) were also investigated and the results indicated that such a structural motif could be a useful approach to the molecular design of highly active two-photon systems for quick-response and related broadband optical-suppressing applications, in particular for confronting laser pulses of a long duration.

11.
Chemistry ; 19(2): 749-60, 2013 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-23169324

RESUMO

A series of star-shaped multi-polar chromophores (compounds 1-3) containing functionalized quinoxaline and quinoxalinoid (indenoquinoxaline and pyridopyrazine) units has been synthesized and characterized for their two-photon absorption (2PA) properties both in the femtosecond and the nanosecond time domain. Under our experimental conditions, these model fluorophores are found to manifest strong and wide-dispersed two-photon absorption in the near-infrared region. It is demonstrated that molecular structures with multi-branched π frameworks incorporating properly functionalized quinoxalinoid units would possess large molecular nonlinear absorptivities within the studied spectral range. Effective optical-power attenuation and stabilization behaviors in the nanosecond time domain of a selected representative dye molecule (i.e., compound 2) from this model compound set were also investigated and the results indicate that such structural motif could be a useful approach for the molecular design toward strong two-photon-absorbing material systems for quick-responsive and broadband optical-suppressing-related applications, particularly to confront long laser pulses.

12.
Nanotechnology ; 23(4): 045303, 2012 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-22222308

RESUMO

In this paper, the high performance GaN-based light-emitting diodes (LEDs) with embedded microscale air voids and an SiO(2) nanomask by metal-organic chemical vapor deposition (MOCVD) were demonstrated. Microscale air voids and an SiO(2) nanomask were clearly observed at the interface between GaN nanorods (NRs) and the overgrown GaN layer by scanning electron microscopy (SEM). From the reflectance spectra we show strong reflectance differences due to the different refractive index gradient between the GaN grown on the nanotemplate and sapphire. It can increase the light extraction efficiency due to additional light scattering. The transmission electron microscopy (TEM) images show the threading dislocations were suppressed by nanoscale epitaxial lateral overgrowth (NELOG). The LEDs with embedded microscale air voids and an SiO(2) nanomask exhibit smaller reverse-bias current and large enhancement of the light output (65% at 20 mA) compared with conventional LEDs.

13.
Surg Neurol ; 72 Suppl 2: S28-34; discussion S34-5, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19665182

RESUMO

BACKGROUND: Because both SCS and HBO therapy have shown some promise in treating patients with states of reduced consciousness, we evaluated the combination of therapies in a prospective trial in comatose patients. METHODS: Twelve patients who had received median nerve stimulation for 3 months without improvement in consciousness received cSCS for 1 year combined with simultaneous HBO therapy for the first 3 months. Another group enrolled 12 patients who received median nerve stimulation only were served as control. RESULTS: Six patients emerged from coma at 1 year (after conclusion of treatment). Glasgow Coma Scale score, SPECT imaging, and PVS scores (state and reaction subscores) of the 12 patients were all significantly increased at 1 year compared with enrollment (P < .05). Neither respirator nor tracheostomy was needed to assist respiration in any patient. Only 1 of 12 patients still needed nasogastric tube feeding at 1 year. By contrast, control patients (without cSCS and HBO therapy) showed no apparent improvement. CONCLUSION: Increase of GCS score, cerebral blood perfusion, and PVS scores were observed in comatose patients treated with combined cSCS and HBO therapy.


Assuntos
Coma/terapia , Terapia por Estimulação Elétrica/métodos , Oxigenação Hiperbárica/métodos , Medula Espinal/cirurgia , Adulto , Biomarcadores , Hemorragia Encefálica Traumática/complicações , Hemorragia Encefálica Traumática/fisiopatologia , Circulação Cerebrovascular/fisiologia , Vértebras Cervicais/cirurgia , Coma/diagnóstico por imagem , Coma/fisiopatologia , Terapia Combinada/instrumentação , Terapia Combinada/métodos , Terapia por Estimulação Elétrica/estatística & dados numéricos , Eletrodos Implantados , Nutrição Enteral/estatística & dados numéricos , Feminino , Escala de Coma de Glasgow , Humanos , Oxigenação Hiperbárica/estatística & dados numéricos , Masculino , Nervo Mediano/fisiologia , Avaliação de Resultados em Cuidados de Saúde , Estudos Prospectivos , Respiração Artificial/estatística & dados numéricos , Medula Espinal/fisiologia , Tomografia Computadorizada de Emissão de Fóton Único , Resultado do Tratamento , Adulto Jovem
14.
Neuromodulation ; 11(4): 296-301, 2008 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22151144

RESUMO

Background. Survival rates after acute brain injury have improved, but persistent coma continues to be a major clinical problem. Objective. We analyzed changes in cerebral perfusion after treatment with right median nerve stimulation (MNS) or MNS with hyperbaric oxygen (MNS + HBO), two noninvasive therapies that have shown promise in this patient population. Methods. During the period this series of patients was treated, decision-makers were offered the option of MNS for six weeks (continued for maximum of three months if patient responded) or MNS + HBO (HBO given during the first six weeks of MNS). Results. Of 41 patients, 14 received MNS only and 27 received MNS + HBO. Pre- and posttreatment single photon emission computed tomography scans showed increased cerebral perfusion in 29 patients, with perfusion unchanged in nine patients and decreased in three patients. A total of 25 patients improved in one or more clinical measures, with 13 regaining consciousness. With univariate analysis, the odds ratio for improvement with MNS + HBO relative to MNS was 4.40 (95% confidence intervals: 1.06-18.36). Multivariate analysis indicated that MNS + HBO was significantly related to increased cerebral perfusion compared with MNS alone (odds ratio = 8.44, 95% confidence intervals: 1.34-52.97). Conclusion. The combination of MNS + HBO is more likely to result in improved cerebral perfusion than MNS alone. Randomized prospective trials evaluating MNS, especially with adjunct HBO, are needed to clarify clinical indications and most effective treatment schemes.

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