Linear Edge Research Articles

A vibration detection system based on two-stage polarization maintaining fiber Sagnac loop fiber laser

A novel fiber grating sensing technique utilized for vibration detection is proposed and experimentally demonstrated. A single wavelength laser is formed by polarization controllers and polarization maintaining fiber (PMF) to construct the high birefringence (Hi-Bi) Sagnac loop, PMF combined with erbium-doped fiber, single mode fiber and polarizer. The cantilever glued to an FBG is used as a sensor probe, and the linear edge of Sagnac ring laser are used to demodulate fiber optic seismic vibration signal. Sagnac ring theory and its edge effects are described in detail, and numerical simulation and experiment show that the vibration signal detection system is adjusted periodically in a range from L1 to L1 + L2, sensitivity goes up to 38.2 W/nm of discrimination, the linearity is 0.9996, and the dynamic range is 4070 dB, these meeting the requirements for vibration detection technical parameters.

Honeycomb frameworks with a very large mesh of 39 × 29 Å diameters stabilized by π-stacked coronene molecules

The assembly of linear edges and triangle nodes in a 3 : 2 molar ratio possibly forms a honeycomb topology: this was achieved by the use of paddlewheel-type dimetal complexes and 2,4,6-tris(4-pyridyl)-1,3,5-triazine, in which the framework with a very large mesh of 39 × 29 Å diameters was stabilized by π-stacked coronene molecules.

External occulter laboratory demonstrator for the forthcoming formation flying coronagraphs

The design and optimization of the external occulter geometry is one of the most discussed topics among solar coronagraph designers. To improve the performance of future coronagraphs and to stretch their inner fields of view toward the solar limb, the new concept of coronagraphs in formation flight has been introduced in the scientific debate. Solar coronagraphs in formation flight require several mechanical and technological constraints to be met, mainly due to the large dimension of the occulter and to the spacecraft's reciprocal alignment. The occulter edge requires special attention to minimize diffraction while being compatible with the handling and integrating of large delicate space components. Moreover, it is practically impossible to set up a full-scale model for laboratory tests. This article describes the design and laboratory tests on a demonstrator for a coronagraph to be operated in formation flight. The demonstrator is based on the principle of the linear edge, thus the presented results cannot be directly extrapolated to the case of the flying circular occulter. Nevertheless, we are able to confirm the results of other authors investigating on smaller coronagraphs and provide further information on the geometry and tolerances of the optimization system. The described work is one of the results of the ESA STARTIGER program on formation flying coronagraphs ["The STARTIGER's demonstrators: toward a new generation of formation flying solar coronagraphs," in 2010 International Conference on Space Optics (ICSO) (2010), paper 39].

Optimal design of short fiber Bragg gratings with triangular spectrum

Based on the mutated adaptive quantum-behaved particle swarm optimization (MAQPSO) algorithm and the discrete layer peeling (DLP) algorithm, we propose a method to design triangular-spectrum fiber Bragg gratings (TS-FBGs). In this method, the DLP algorithm is used to generate an appropriate initial range of the index modulation, and the MAQPSO technique is applied to optimize the index modulation within this range. The quantum-behaved particle swarm optimization algorithm with mutation operation can improve the search performance of this algorithm. We purposely use a linear weighting factor for the fitness value function in view of the linear edge triangular-spectrum. This dramatically accelerates the convergence in the numerical implementation. Using the proposed method, a 0.2 nm bandwidth TS-FBG is designed and the performance is shown to be better than previously reported results in the literature. Then, a 2.5 nm bandwidth TS-FBG is reconstructed; it is indicated that a short grating length can be used to realize the TS-FBG with chirp-free structure so that complex phase modulation is avoided in fabrication. Finally, a triple-channel TS-FBG with sampled-free structure is successfully designed and optimized. We also present an analysis on the tolerance of the design method over possible fabrication error.

Nail digital dermoscopy (Onychoscopy) in the diagnosis of onychomycosis

Distal subungual onychomycosis and traumatic onycholysis are the most common causes of toenail abnormalities, and differential diagnosis is often impossible without mycology. To identify and describe dermoscopic signs specific for distal subungual onychomycosis that could facilitate its diagnosis and differentiation from traumatic mycologically negative onycholysis and to determine the sensitivity and specificity of these dermoscopic features. We performed a retrospective study at the Outpatient Consultation for Nail Diseases of the Department of Dermatology of the University of Bologna. Dermoscopic digital images of 57 consecutive patients who underwent global photography, videodermoscopy and mycological examination for onycholysis of a single toenail between 1 December, 2010 and 30 June, 2011, were evaluated and compared. Digital dermoscopic images of onycholysis of the great toenail were evaluated for the presence of peculiar dermoscopic features. The presumptive dermoscopic diagnosis was compared with results of mycology. Evaluation of videodermoscopic images allowed us to identify three recurring peculiar dermoscopic features, two of which were present only in distal subungual onychomycosis (jagged proximal edge with spikes of the onycholytic area and longitudinal striae) and one only in traumatic onycholysis (linear edge - without spikes - of the onycholytic area). We found distinctive dermoscopic signs that are exclusive to distal subungual onychomycosis and to traumatic onycholysis. Detection of these signs is simple and can, in selected cases, help to avoid mycology.

Effect of the size of the pupae, adult diet, oviposition substrate and adult population density on egg production in Musca domestica (Diptera: Muscidae)

In order to enhance the mass production of the house fly, Musca domestica, five aspects of its oviposition biology were analyzed. Oviposition substrate and the manner of its presentation, the composition of the diet of the adults, size of the pupae and numbers of flies in a cage were identified as critical. Females preferred to lay eggs on a substrate which was presented within a shelter and with increased linear edges against which the flies could oviposit. Different types of oviposition substrate resulted in comparable yields of eggs. The presence of an oviposition attractant (ammonia) in the manure was found to have a potentially posi- tive effect on female fecundity. Egg yield increased when two protein sources (yeast and milk) were included in the adult diet. How- ever, flies fed a mixture of sugar and yeast laid over 50% fewer eggs than those fed the same proportion of sugar and milk. The fecundity of flies decreased with increase in the number of flies per cage, but the highest total number of eggs per cage was obtained when the flies were most crowded (14.2 cm 3 per fly). The size of the pupae did not significantly affect egg production.

Use of Salient Features for the Design of a Multistage Framework to Extract Roads From High-Resolution Multispectral Satellite Images

The process of road extraction from high-resolution satellite images is complex, and most researchers have shown results on a few selected set of images. Based on the satellite data acquisition sensor and geolocation of the region, the type of processing varies and users tune several heuristic parameters to achieve a reasonable degree of accuracy. We exploit two salient features of roads, namely, distinct spectral contrast and locally linear trajectory, to design a multistage framework to extract roads from high-resolution multispectral satellite images. We trained four Probabilistic Support Vector Machines separately using four different categories of training samples extracted from urban/suburban areas. Dominant Singular Measure is used to detect locally linear edge segments as potential trajectories for roads. This complimentary information is integrated using an optimization framework to obtain potential targets for roads. This provides decent results in situations only when the roads have few obstacles (trees, large vehicles, and tall buildings). Linking of disjoint segments uses the local gradient functions at the adjacent pair of road endings. Region part segmentation uses curvature information to remove stray nonroad structures. Medial-Axis-Transform-based hypothesis verification eliminates connected nonroad structures to improve the accuracy in road detection. Results are evaluated with a large set of multispectral remotely sensed images and are compared against a few state-of-the-art methods to validate the superior performance of our proposed method.

Edge plasmons in graphene nanostructures

Plasmon modes in graphene are influenced by the unusual dispersion relation of the material. For bulk plasmons this results in a n(1/4) dependence of the plasma frequency on the charge density, as opposed to the n(1/2) dependence in two-dimensional electron gas (2DEG); yet, bulk plasmon dispersion in graphene follows a similar q(1/2) behavior as for other two-dimensional materials. In this work we consider finite graphene nanostructures, semi-infinite sheets, and circular disks and study edge plasmons that are confined to the boundaries of the structures. We find that, for abrupt edges, graphene edge plasmons behave analogously to those in 2DEGs, but, for gradual edge profiles, important distinctions arise. In particular, we show that for a linear edge profile, graphene supports fewer edge modes than a 2DEG at a given q, and the edge monopole plasmon dispersion in graphene follows a q(1/4) law in contrast to the q(0) behavior seen in 2DEGs. RAMOWITZ M, 1964

Quantitative measurement of the homogeneity and contrast of step edges in the estimation of the point spread function of a satellite image

It is important to measure the spatial performance of an in-flight satellite sensor to determine if any spatial resolution degradations occur over time; then some compensation methods can be adopted to improve the image quality. In satellite on-orbit measurements of spatial resolution, the performance of the sensors can be objectively evaluated through the point spread function (PSF) or modulation transfer function (MTF). The well-known image-based PSF derivation method of sampling along a slanted linear step structure from the degraded image is widely used in the satellite image restoration area. Due to the non-uniformity of the linear ground objects, generally, the operators have to pick out good profiles from all the profiles along the edge in order to increase the estimation accuracy. However, only some qualitative criteria have been proposed in the literature to instruct researchers how to pick out good profiles. In this article, we propose a method to quantitatively measure the homogeneity and contrast of the candidate linear structures in order to extract the optimal profiles. This method first automatically detects and locates the slanted linear step edge object in the image. Then it measures the homogeneity and the contrast at each location along the edge by using two adjacent square regions on both sides of the linear step structure. The locations that have high measurement values are regarded as the optimal locations. Finally, the optimal profiles can be extracted at these edge locations to derive an accurate PSF estimation by differentiation. This method makes an automatic optimal step edge detection method for PSF derivation to be practical. Experiment results on simulated and real images are provided. This article shows that using only the ‘optimal’ profiles can play a real and important role and can achieve a good PSF estimation result.

Development of low-noise centrifugal fans for a refrigerator using inclined S-shaped trailing edge

Low-noise centrifugal fans are developed by modifying the linear trailing edge lines of the fan blades into inclined S-shaped lines. The noise reductions achieved by using the inclined S-shaped trailing edges in the existing fans are confirmed by comparing the predicted BPF noise components of the developed fans with those of the existing fan. In addition, the turbulent kinetic energy of the fluid for the inclined S-shaped fans is predicted to be less than that for the existing fan. Finally, experiments using four prototype fans show that the levels of broadband noise from the newly developed fans are less than those of noise from existing fans. An additional experiment performed by using a selected low-noise fan installed in a household refrigerator show that the overall noise from the new fan is reduced by approximately 2.2 dB in comparison with that from the existing fan in the refrigerator.

Linear edge and temperature characteristic of tilted fiber Bragg gratings cladding-mode envelope

In this paper, a system of linear edge filter demodulation based on weakly tilted fiber Bragg gratings in fiber sensor was proposed. The linear edge of the cladding-mode envelope and temperature characteristic between cladding modes and core mode of tilted fiber Bragg grating (TFBG) were experimentally investigated. The results show that falling edge (1505–1535 nm) and rising edge (1545–1565 nm) of the cladding-mode envelope is approximately linear and can be used as an edge filter. Moreover, the temperature characteristics of the core mode and cladding modes are similar to FBG’s. It can dynamically compensate the temperature induced wavelength shift of the FBG and the effect of temperature on the demodulated sensing signals is minimized. The advantages of this simple system are an all-fiber design, quasi static and dynamic operation, high stability and lower cost.

Image Shrinkage Based on Hot-Target Map and Featured Edge Preservation

图像收缩是缩小高分辨率图像以适应不同纵横比小尺寸显示屏幕的过程,关键是收缩后能够凸显图像重要区域,保持连续,避免扭曲.提出一种新的图像收缩方法,该方法首先基于能量失真约束,迭代收缩覆盖图像的四边形网格至目标大小,然后映射,插值目标网格实现图像收缩.能量失真反映了对重要区域的凸显程度、结构的保持效果以及扭曲避免情况,失真越小,目标图像越理想.在该约束下,构成网格的子四边形非均匀收缩,重要度大的收缩小.为准确计算子四边形的重要度,根据图像显著度和边缘构建反映图像重要度的Hot-Target 图.最后,通过保持图像直线边,称为特征边缘,避免非均匀收缩引起的边缘扭曲.为提高效率,降低复杂度,该方法由迭代求解线性方程实现.实验结果验证了方法的有效性.

Image Spread Spectrum Watermark Technique Based on Digital Holography and Ridgelet Transform

A novel image watermarking algorithm based on digital holography and ridgelet transform was designed by taking the advantage that ridgelet transform domain is a most suitable representation of image’s linear outline edge features. Firstly, the image was divided into blocks, and each block was transformed by finite ridgelet transformation. Secondly, the digital holography watermark that is got with the spread spectrum technique is embedded into the most energetic coefficients of ridgelet . A correlation function is used in the watermark detection process and the original image is not required.Experimen result show the watermark is robust to noise,medial filtering and JPEG2000 lost compression.By comparating respectively with paper[4] and paper[5],the result shows the proposed algorithm is more superior to them.

Comparative evaluation of noise insensitivity of linear edge detection techniques

This work presents a comparative estimate of white-noise insensitivity of the most requested linear edge detection techniques dealing with grayscale images. We consider detectors based on the first and second derivatives of the image brightness. The comparative evaluation was based on statistical analysis. The Kirsh and Frei-Chen operators were found to be less sensitive to noise.

A cohesive edge crack

The nucleation and growth of a cohesive edge crack is studied. This topic is germane to the initiation and early stage of crack growth during unnotched beam testing, the growth of short edge cracks in finite test pieces, and the formation of tension cracks of geological origin. This paper focuses on an edge crack in a semi-infinite plane, under a uniform far-field tensile stress acting parallel to the plane boundary. Expressions for the Mode I stress-intensity-factor and crack-opening-displacement for an edge crack subjected to arbitrary crack face loading are determined via the weight function method. All of the constants needed to define the weight function and associated integrals are themselves explicit functions of just two constants: f r and ψ. Two types of softening behavior in the cohesive zone are examined: rectangular softening, and linear softening. In each case the process zone size, energy-release-rate, crack-opening displacement and load-ratio are examined. The different test behavior exhibited under load-control versus fixed-grip displacement control is explored. The test control conditions alter the fracture behavior significantly. For a linear softening cohesive edge crack, it is found out that under fixed-grip control (load-control), the process zone size decreases (increases) steadily with increasing traction-free crack length, approaching the semi-infinite crack asymptote from above (below). The differences between load-control versus fixed-grip control decrease rapidly with increasing traction-free crack length.

Macroscopic single‐domain graphene sheet on Ni(111)

We observed in situ growth of a single graphene sheet on Ni(111) by low‐energy electron microscopy. The sheet was grown epitaxially beyond the steps on the substrate. The crystalline shapes of graphene islands were clearly seen; the straight edges of the island are crossed at either 60 or 120°, and the linear edges shifted perpendicular to the edge keeping the equilibrium shape. Graphene islands were united to form a single sheet without any grain boundaries and any wrinkles. The Ni substrate of several centimeters in size was covered with a single‐domain graphene sheet. Copyright © 2011 John Wiley & Sons, Ltd.

Bat habitat use in logged jarrah eucalypt forests of south‐western Australia

Summary 1. Ecologically sustainable forest management is being implemented to address the competing demands of timber production and conservation, but its effectiveness is poorly understood. Bats play key roles in forest ecosystems and are sensitive to timber harvesting, so are potential indicators of whether management is successfully achieving biodiversity conservation in production forests. 2. We evaluated logging impacts in jarrah eucalypt forests of south‐western Australia by examining insectivorous bat activity, feeding buzzes and insect biomass at four sites in each of recently logged forest, young regrowth and old regrowth. 3. Forest tracks supported higher overall activity and higher feeding activity than off‐track sites, but activity was similar on‐track irrespective of logging history. However, off‐track activity in old regrowth was significantly higher than in either young regrowth or recently logged forest. 4. Vespadelus regulus and Nyctophilus spp. were more active in old regrowth than other logging histories. Similarly, V. regulus, Nyctophilus spp., Chalinolobus gouldii, Chalinolobus morio and Falsistrellus mackenziei activity was significantly greater on‐ than off‐tracks, but activity was similar on‐track across logging histories. 5. Increased understorey clutter was the strongest predictor of reduced bat activity in off‐track sites. Reduced clutter and roost availability most probably explained greater activity in old regrowth forest. Neither insect biomass nor interactive effects of clutter and insect biomass significantly affected bat activity. 6. Synthesis and applications. Tracks provided internal linear edges within cluttered forests allowing bat species to use such areas for foraging. However, our results suggest that the retention of unlogged areas within logged forests is likely to be the most effective strategy in many forest ecosystems for conserving bat populations and achieving ecologically sustainable forest management for this group.

Demodulation of the FBG temperature sensor with the tunable twin‐core fiber

AbstractA novel linear edge filter based on a piece of tunable twin‐core fiber is proposed in this article.The transmission spectrum of the twin‐core fiber can be adjusted by pulling and twisting the twin‐core fiber to match the central wavelength of the Fiber Bragg Grating (FBG) used for the temperature sensor. The feasibility of the method is analyzed and demonstrated experimentally. This demodulation filter, which is based on the all‐fiber component, can be designed and adjusted according to the measurement sensitivity and range of FBG temperature sensor, so its characteristics of compact scheme and low cost would make this method more applicable. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:81–84, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25681

A Novel Method of Sub-Pixel Linear Edge Detection Based on First Derivative Approach

In this paper, a novel algorithm is proposed to detect linear edge. Image gradient is acquired by Sobel or Prewitt filters. Logical addition is applied to enhance image contrast. Statistical method is employed to cope with gradient data—gradient projection in the horizontal and vertical direction to compute the average gradient value. Multi-level B-Spline interpolation is employed to smooth gradient data. At last, edge coordinates can be computed precisely by the number and interval of extreme points. The experiment results are presented to show validity of the algorithm, which precision and accuracy can reach to sub-pixel. The proposed approach puts merits of zero crossing method and threshold method together, which is very robust, convenient and efficient to detect linear edge in industrial environment.

Coulomb drag between helical edge states

We theoretically investigate the Coulomb drag between the edge states of two quantum spin Hall systems. Using an interacting theory of the one-dimensional helical edge modes, we show that the drag vanishes at second order in the inter-edge interaction, where it is typically finite in other systems, due to the absence of backscattering within the edges. However, in the presence of a small external magnetic field the drag is finite and scales as the fourth power of the magnetic field, a behavior that sharply distinguishes it from other systems. We obtain the temperature dependence of the drag for regimes of both linear and quadratic edge dispersion in the presence of a finite field.