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1.
Sci Total Environ ; 712: 136509, 2020 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-31931202

RESUMO

Driven by increasing urban demand, spatially-varying urban expansion has led to significant ecosystem degradation in China and elsewhere. Spatial nonstationarity affects the relationship between urban expansion and ecosystem service value (ESV) loss, but its significance has been under-emphasized. To study the spatially-heterogeneous ESV loss, we integrated cellular automata (CA) with geographically weighted regression (GWR) in a model that considers the relationships between urban expansion and its driving factors. We used ten GWR bandwidths to construct the CAGWR models for reproducing rapid urban expansion at Chongqing from 2005 to 2010. We then used the CAGWR model with the best bandwidth to predict future urban scenarios out to 2030. Our modeling shows that CAGWR is strongly sensitive to bandwidth, and that the overall accuracy and Figure-of-Merit are maximized with a ~2 km2 bandwidth (about 150 samples). We examined ESV losses in eleven ecosystem classes and found that climate regulation and water flow regulation are the dominant drivers of ESV loss. From 2010 to 2030, Chongqing's urban area will increase by about 87%, resulting in substantial encroachment on agricultural land, dryland and shrubs, causing significant ESV losses of about 38%. Our results constitute an early warning of ecosystem degradation caused by massive urban development. This study improves our understanding of spatially-varying urban expansion and related ESV losses in rapidly developing areas and should help improve urban planning regulation and regional policy for sustainable development to maintain environmentally-friendly cities.

2.
Appl Opt ; 58(36): 9861-9869, 2019 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-31873631

RESUMO

It is important to enhance the contrast and remove the speckle noise for optical coherence tomography (OCT) images. In this paper, we propose a selective retinex enhancement method based on the fuzzy c-means (FCM) clustering algorithm to enhance only the structure part in OCT images and combines with the block-matching 3D (BM3D) algorithm for filtering. In the proposed selective retinex enhancement method, we first calculate the feature image of the original image, which includes the mean value and standard deviation of each pixel in the original image and its correlation image. Second, by applying the FCM clustering algorithm to the feature image, a mask is generated that can distinguish the structure part from the background part in the OCT image. Then, the mask is applied to the multi-scale retinex algorithm, and only the structure part in the OCT image is enhanced. Moreover, the BM3D method is applied to filter the enhanced image. Experimental results demonstrate that the proposed method performs impressively in improving the contrast and removing the speckle noise of OCT images, and it provides better quantitative performance in terms of signal-to-noise ratio, contrast-to-noise ratio, equivalent number of looks, and the edge preservation parameter $ \beta $ß.

3.
Opt Express ; 27(22): 32378-32391, 2019 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-31684452

RESUMO

The fringe skeleton method is the most straightforward analysis method for phase extraction and widely used in dynamic measurement. Binarization is often required in this method. In the traditional binarization methods, filtering is often a necessary step prior to binarization due to the influence of intrinsic speckle noises in ESPI fringe patterns. In this paper, we propose a binarization method based on local entropy and fuzzy c-means (FCM) clustering algorithm. In this method, the pixels in the given ESPI fringe pattern are clustered into white fringes and black fringes according to their local entropy instead of the original intensity information. There is no need to perform the filtering preprocessing, because the intrinsic speckle noises are utilized as essentials. We evaluate the performance of our method by applying it to the computer-simulated and real fringe patterns. Experimental results demonstrate that the proposed method can achieve the desired binarization results, and the binarization results can give desired skeleton results.

4.
Appl Opt ; 58(27): 7523-7530, 2019 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-31674404

RESUMO

The fringe orientation is an important feature of the electronic speckle interferometry (ESPI) fringe pattern. Accurate and efficient calculation of the fringe orientation is very important for subsequent electronic speckle processing such as skeleton extraction and image filtering. To accurately and efficiently estimate fringe orientation, we propose an effective method based on a convolutional neural network. In the proposed method, the network needs clean-noisy image pairs to train and noisy images with theoretical value to test. The aligned noise-free ESPI fringe pattern orientation fields are fairly good estimations for the corresponding noise ones. After the model training is done, the other multiple ESPI fringe patterns are fed to the trained network simultaneously; the corresponding orientation results can be obtained accurately and efficiently. The advantage of using this method to extract the orientation is that the fringe orientation information can be extracted accurately and efficiently without complicated parameter adjustment. We evaluate the performance of our method via applying our method to the computer-simulated and experimentally acquired ESPI fringe patterns and comparing the results with those of three extensively used methods.

5.
Appl Opt ; 58(23): 6233-6243, 2019 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-31503765

RESUMO

In this paper, we propose a total variation based on block matching 3D (BM3D-TV method), which includes the total variation regular term, the data fidelity term, and the block matching term. In addition, we also propose a fast numerical algorithm based on the split Bregman iteration for the proposed method. By assigning suitable weights to the data fidelity term and block matching term, the image noise reduction and the image structural characteristics can be matched optimally. We test the proposed method on six human retinal and one mouse skin optical coherence tomography (OCT) images respectively, and also compare it with total variation (TV) and BM3D, which were proved to be effective in denoising. The performances of these methods are quantitatively evaluated in terms of the signal-to-noise ratio, the contrast-to-noise ratio, and the averaged equivalent number of homogeneous areas at the aspects of speckle reduction and structure protection. Vast experiments show that the BM3D-TV method can effectively reduce speckle noise in OCT images, protect important structural information and improve image quality, compared with the BM3D and TV methods.

6.
Appl Opt ; 58(13): 3338-3346, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-31044829

RESUMO

The denoising of electronic speckle pattern interferometry (ESPI) fringe patterns is a key step in the application of ESPI. In this paper, we propose a method for batch denoising of ESPI fringe patterns based on a convolution neural network (CNN). In the proposed method, the network is first trained by our training dataset, which consists of the noisy ESPI fringe patterns and the corresponding noise-free images. We propose a new computer-simulated method of ESPI fringe patterns to create our training dataset. After training, the other multi-frame ESPI fringe patterns to be processed are fed to the trained network simultaneously, and the corresponding denoising images can be obtained in batches. We demonstrate the performance of the proposed method via application to 50 computer-simulated ESPI fringe patterns and three groups of experimentally obtained ESPI fringe patterns. The experimental results show that our method can obtain desired results even when the quality of ESPI fringe images is considerably low because of variable density, high noise, and low contrast, and our method can denoise multi-frame fringe patterns simultaneously. Moreover, we use the computer-simulated ESPI fringe patterns to train the network; after training, the trained network can be used to denoise either computer-simulated ESPI fringe patterns or the experimentally obtained ESPI fringe patterns. The proposed method is especially suitable for processing a large number of ESPI fringe patterns.

7.
Environ Monit Assess ; 191(5): 291, 2019 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-31001709

RESUMO

Quantifying the contribution of driving factors is crucial to urban expansion modeling based on cellular automata (CA). The objective of this study is to compare individual-factor-based (IFB) models and multi-factor-based (MFB) models as well as examine the impacts of each factor on future urban scenarios. We quantified the contribution of driving factors using a generalized additive model (GAM), and calibrated six IFB-DE-CA models and fifteen MFB-DE-CA models using a differential evolution (DE) algorithm. The six IFB-DE-CA models and five MFB-DE-CA models were selected to simulate the 2005-2015 urban expansion of Hangzhou, China, and all IFB-DE-CA models were applied to project future urban scenarios out to the year 2030. Our results show that terrain (DEM) and population density (POP) are the two most influential factors affecting urban expansion of Hangzhou, indicating the dominance of biophysical and demographic drivers. All DE-CA models produced defensible simulations for 2015, with overall accuracy exceeding 89%. The IFB-DE-CA models based on DEM and POP outperformed some MFB-DE-CA models, suggesting that multiple factors are not necessarily more effective than a single factor in simulating present urban patterns. The future scenarios produced by the IFB-DE-CA models are substantially shaped by the corresponding factors. These scenarios can inform urban modelers and policy-makers as to how Hangzhou city will evolve if the corresponding factors are individually focused. This study improves our understanding of the effects of driving factors on urban expansion and future scenarios when incorporating the factors separately.


Assuntos
Monitoramento Ambiental/métodos , Modelos Teóricos , Urbanização/tendências , Algoritmos , China , Cidades , Previsões
8.
Appl Opt ; 58(6): 1442-1450, 2019 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-30874029

RESUMO

The filtering of ESPI fringe patterns with both noise and discontinuity is a challenging problem raised in recent years. Discontinuity-detectable and discontinuity-aware processing techniques are demanded. In this paper, a fuzzy c-means (FCM) clustering based fringe segmentation method is proposed. By applying the FCM clustering method to the estimated fringe orientation, we segment the discontinuous ESPI fringe patterns into continuous segments, thus the discontinuous region is identified and a discontinuous region mask is generated. Then, the discontinuous region mask is introduced into the controlling speed function, and an adaptive shape-preserving oriented partial differential equation (OPDE) model is proposed for discontinuous ESPI fringe patterns denoising. According to our method, the discontinuous regions are effectively found and with the proposed adaptive shape-preserving OPDE, the noise is well eliminated, the shape of fringes and the discontinuity are well kept. The performance of our method is illustrated with three computer-simulated and one experimentally obtained discontinuous ESPI fringe patterns and comparison with related segmentation methods and OPDEs.

9.
Appl Opt ; 58(2): 219-226, 2019 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-30645297

RESUMO

Phase unwrapping is one of the key steps of optical interferogram analysis, among which phase discontinuity is still a challenge. In this paper, we propose a new weighted least-squares phase-unwrapping algorithm for discontinuous optical phase patterns. In the proposed algorithm, the orientation coherence is introduced to define the new weighting coefficient, which can accurately show the wrapped phase quality. According to our proposed algorithm, the new weighting coefficient has a good performance on distinguishing the continuous regions and the discontinuous regions in wrapped phase patterns. This advantage of our algorithm can ensure a more reliable unwrapped result for discontinuous optical phase patterns. We test the proposed algorithm on the computer-simulated speckle phase images and two experimentally obtained phase images, respectively, and compare them with the other five widely used methods. The experimental results demonstrate the performance of our new weighted least-squares phase-unwrapping algorithm.

10.
Ultrasonics ; 92: 13-20, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30216781

RESUMO

Lamb waves and electro-mechanical impedance (EMI) based methods are increasingly used in damage detection owing to their high sensitivity to small structural defects. Lamb wave based methods are effective in detecting damages in a large area and electro-impedance based methods are suitable for characterizing the identified damage. Based on these two methods, a novel combined damage detection method is presented in this research. To achieve this, first, a mobile transducer set is developed, which can be used for both the Lamb waves and EMI based methods. Then, a baseline-free damage detection strategy that combines the Lamb waves and EMI methods is presented. Finally, a laboratory-sized test piece is used to validate the effectiveness of the proposed approach. The results achieved with the application of the presented combined method for characterizing an L-shape crack in an aluminum plate show better location accuracy and detection efficiency than those obtained by applying only one method.

11.
J Biomech ; 73: 161-167, 2018 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-29650411

RESUMO

Biological composite materials, such as bone, tooth and nacre, are comprised of a mixture of nano-sized hard components (e.g. mineral platelets) and soft components (e.g. protein molecules). Their mechanical behaviour greatly depends on the protein-mineral interfaces. This paper investigates the effects of mineral surface nanostructures on the interfacial interaction and mechanical behaviour of protein-mineral nanocomposites. Interfacial shear between osteopontin (OPN) and hydroxyapatite (HA) mineral layers with surface nanostructures is investigated using the atomistic molecular dynamics (MD) simulations. The results indicate that the OPN residues can be attached to HA surfaces but the surface nanostructures greatly affect the interfacial interaction and mechanical behaviour. The HA layers with a higher number of nano-sized grooves (defects) increase the surface roughness but reduce the pulling force and energy dissipation.


Assuntos
Durapatita/química , Fenômenos Mecânicos , Simulação de Dinâmica Molecular , Nanocompostos/química , Osteopontina/química , Dureza , Conformação Proteica
12.
Appl Opt ; 57(4): 861-871, 2018 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-29400751

RESUMO

In this paper, we propose an image decomposition model Shearlet-Hilbert-L2 with better performance for denoising in electronic speckle pattern interferometry (ESPI) fringe patterns. In our model, the low-density fringes, high-density fringes, and noise are, respectively, described by shearlet smoothness spaces, adaptive Hilbert space, and L2 space and processed individually. Because the shearlet transform has superior directional sensitivity, our proposed Shearlet-Hilbert-L2 model achieves commendable filtering results for various types of ESPI fringe patterns, including uniform density fringe patterns, moderately variable density fringe patterns, and greatly variable density fringe patterns. We evaluate the performance of our proposed Shearlet-Hilbert-L2 model via application to two computer-simulated and nine experimentally obtained ESPI fringe patterns with various densities and poor quality. Furthermore, we compare our proposed model with windowed Fourier filtering and coherence-enhancing diffusion, both of which are the state-of-the-art methods for ESPI fringe patterns denoising in transform domain and spatial domain, respectively. We also compare our proposed model with the previous image decomposition model BL-Hilbert-L2.

13.
Appl Opt ; 56(16): 4843-4853, 2017 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-29047624

RESUMO

Filtering off speckle noise from a fringe image is one of the key tasks in electronic speckle pattern interferometry (ESPI). In general, ESPI fringe images can be divided into three categories: low-density fringe images, high-density fringe images, and variable-density fringe images. In this paper, we first present a general filtering method based on variational image decomposition that can filter speckle noise for ESPI fringe images with various densities. In our method, a variable-density ESPI fringe image is decomposed into low-density fringes, high-density fringes, and noise. A low-density fringe image is decomposed into low-density fringes and noise. A high-density fringe image is decomposed into high-density fringes and noise. We give some suitable function spaces to describe low-density fringes, high-density fringes, and noise, respectively. Then we construct several models and numerical algorithms for ESPI fringe images with various densities. And we investigate the performance of these models via our extensive experiments. Finally, we compare our proposed models with the windowed Fourier transform method and coherence enhancing diffusion partial differential equation filter. These two methods may be the most effective filtering methods at present. Furthermore, we use the proposed method to filter a collection of the experimentally obtained ESPI fringe images with poor quality. The experimental results demonstrate the performance of our proposed method.

14.
Bioinspir Biomim ; 11(5): 056004, 2016 08 16.
Artigo em Inglês | MEDLINE | ID: mdl-27529133

RESUMO

Open surgery is currently the main treatment method for the lumbar burst fracture with neurological deficit but may irreversibly disrupt the lumbar anatomy. The minimally invasive surgery (MIS) techniques have recently gained increasing attention. However, their use is still limited to lumbar burst fractures mainly due to their difficulties in burst fracture reduction and decompression. Here we present a novel bio-inspired MIS device which can be used with an endoscope to reset the bone fragments retropulsed into the spinal canal within the wounded vertebral body. Its head jaw mimics the biomechanical characteristics of a crocodile rostrum to improve the performance in gripping and moving bone pieces in the confined space of a vertebral body. This study may be capable of converting the posterior open surgeries to the MIS procedures, and expands the use of the MIS techniques in the treatment of lumbar burst fractures.


Assuntos
Jacarés e Crocodilos , Materiais Biomiméticos , Fixação de Fratura/métodos , Fraturas Cominutivas/cirurgia , Vértebras Lombares/lesões , Crânio/anatomia & histologia , Fraturas da Coluna Vertebral/cirurgia , Animais , Fenômenos Biomecânicos , Descompressão Cirúrgica/instrumentação , Descompressão Cirúrgica/métodos , Desenho de Equipamento/métodos , Humanos , Arcada Osseodentária/anatomia & histologia , Arcada Osseodentária/fisiologia , Crânio/fisiologia
15.
Opt Express ; 23(21): 28067-75, 2015 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-26480464

RESUMO

An updated B-scan method is proposed for measuring the evolution of thermal deformation fields in polymers. In order to measure the distributions of out-of-plane deformation and normal strain field, phase-contrast spectral optical coherence tomography (PC-SOCT) was performed with the depth range and resolution of 4.3 mm and 10.7 µm, respectively, as thermal loads were applied to three different multilayer samples. The relation between temperature and material refractive index was predetermined before the measurement. After accounting for the refractive index, the thermal deformation fields in the polymer were obtained. The measured thermal expansion coefficient of silicone sealant was approximately equal to its reference value. This method allows correctly assessing the mechanical properties in semitransparent polymers.

16.
ScientificWorldJournal ; 2014: 282436, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24977189

RESUMO

Recent advances of interfacial micromechanics in fiber reinforced composites using micro-Raman spectroscopy are given. The faced mechanical problems for interface design in fibrous composites are elaborated from three optimization ways: material, interface, and computation. Some reasons are depicted that the interfacial evaluation methods are difficult to guarantee the integrity, repeatability, and consistency. Micro-Raman study on the fiber interface failure behavior and the main interface mechanical problems in fibrous composites are summarized, including interfacial stress transfer, strength criterion of interface debonding and failure, fiber bridging, frictional slip, slip transition, and friction reloading. The theoretical models of above interface mechanical problems are given.


Assuntos
Adesivos/química , Manufaturas , Modelos Químicos , Polímeros/química , Adesividade , Força Compressiva , Simulação por Computador , Módulo de Elasticidade , Fricção , Dureza , Teste de Materiais , Resistência ao Cisalhamento , Estresse Mecânico , Resistência à Tração
17.
Guang Pu Xue Yu Guang Pu Fen Xi ; 33(5): 1244-8, 2013 May.
Artigo em Chinês | MEDLINE | ID: mdl-23905328

RESUMO

The present paper studied the methodology of carbon nanotube (CNT) sensor applicable for the strain measurement in microscale. Based on the varieties of polarization configurations of the Raman spectrometers, a series of analytic expressions of CNT sensor were derived by applying the Raman properties of the CNT, such as the strain sensitivity and the polarization selectivity. From the viewpoint of metrology, the sensoring relationships corresponding to different polarization configurations were compared and contrasted with one another, which educed that the "bipolar homology" type is most suitable for the strain measurement where both the incident and scattered lights are continuously controllable and always remain parallel to each other. A new easy-realized control method for this configuration is introduced. The experiments proved that the method presented in this paper can effectively measure the in-plane strain components in microscale by polarized micro-Raman spectroscopy.

18.
Appl Spectrosc ; 67(6): 600-5, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23735244

RESUMO

The interfacial stress transfer behavior of a Kevlar 49 aramid fiber-epoxy matrix was studied with fiber pullout tests, the fibers of which were stretched by a homemade microloading device. Raman spectra on the embedded fiber were recorded by micro-Raman spectroscopy, under different strain levels. Then, the fiber axial stress was obtained by the relationship between the stress and Raman shift of the aramid fiber. Experimental results revealed that the fiber axial stress increased significantly with the load. The shear stress concentration occurred at the fiber entry to the epoxy resin. Thus, interfacial friction stages exist in the debonded fiber segment, and the interfacial friction shear stress is constant within one stage. The experimental results are consistent with the theoretical model predictions.

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