Gamma Transformation Research Articles

Efficient OCT Image Enhancement Based on Collaborative Shock Filtering.

Efficient enhancement of noisy optical coherence tomography (OCT) images is a key task for interpreting them correctly. In this paper, to better enhance details and layered structures of a human retina image, we propose a collaborative shock filtering for OCT image denoising and enhancement. Noisy OCT image is first denoised by a collaborative filtering method with new similarity measure, and then the denoised image is sharpened by a shock-type filtering for edge and detail enhancement. For dim OCT images, in order to improve image contrast for the detection of tiny lesions, a gamma transformation is first used to enhance the images within proper gray levels. The proposed method integrating image smoothing and sharpening simultaneously obtains better visual results in experiments.

Cu partitioning behavior and its effect on microstructure and mechanical properties of 0.12C-1.33Mn-0.55Cu Q&P steel

Cu, as an austenitic stable element, is added to steel in order to suppress the adverse effects of high content of C and Mn on welding. Based on C partitioning, Cu and Mn partitioning can further improve the stability of retained austenite in the intercritical annealing process. A sample of low carbon steel containing Cu was treated by the intercritical annealing, then quenching process (I&Q). Subsequently, another sample was treated by the intercritical annealing, subsequent austenitizing, then quenching and partitioning process (I&Q&P). The effects of element partitioning behavior in intercritical region on the microstructure and mechanical properties of the steel were studied. The results showed that after the I&Q process ferrite and martensite could be obtained, with C, Cu and Mn enriched in the martensite. When intercritically heated at 800 degrees C, Cu and Mn were partitioned from ferrite to austenite, which was enhanced gradually as the heating time was increased. This partitioning effect was the most obvious when the sample was heated at 800 degrees C for 40 min. At the early stage of alpha -> gamma transformation, the formation of. was controlled by the partitioning of carbon, while at the later stage, it was mainly affected by the partitioning of Cu and Mn. After the I&Q&P process, the partitioning effect of Cu and Mn element could be retained. C was assembled in retained austenite during the quenching and partitioning process. The strength and elongation of I&Q&P steel was increased by 5 305 MPa% compared with that subjected to Q&P process. The volume fraction of retained autensite was increased from 8.5% to 11.2%. Hence, the content of retained austenite could be improved significantly by Mn and Cu partitioning, which increased the elongation of steel.

Effect of inorganic acid on the phase transformation of alumina

This paper focused on the effect of hydrochloric acid and nitric acid on phase transformation of gamma to alpha alumina. The microstructure, phase composition of specimens and crystallite sizes of α-Al2O3 are investigated by X-ray diffraction, SEM, Scherrer formula and external standard method. The results showed that the phase transitions of alumina was affected by the kinds and concentrations of inorganic acid. Hydrochloric acid was more advantageous to promote the transformation of γ-alumina to α-alumina than nitric acid above 900 °C. In addition, the α-fraction of specimens obtained by Al2O3-HCl gels increased from 71.0% to 87.1% after calcination at 1000 °C when acid concentration increased from 0.1*10-4 mol/L to 0.1mol/L. On the contrary, the α-fraction of specimens obtained by Al2O3-HNO3 gels decreased from 79.4% to 73.9%. And at 1100 °C up to nearly 100% of α-alumina in the specimens was obtained. Moreover, both hydrochloric acid and nitric acid were beneficial to the growth of the crystallite sizes of prepared α-Al2O3. Meanwhile the effect of hydrochloric acid on the phase transitions of alumina was further promoted by employing a two-step heat-treatment method. XRD and SEM confirmed that the first-step heat-treatment played an important role in the course of the calcination processes for low-temperature of α-alumina formation.

Heat treatment effect on crystal structure and design of highly sensitive room temperature CO2 gas sensors using anodic Bi2O3 nanoporous formed in a citric acid electrolyte

The effect of annealing temperature on the crystal structure of anodic bismuth trioxide (ABO) layers prepared via anodization in a citric acid-based electrolyte was studied. The samples were annealed in air at temperatures ranging from 200 °C to 600 °C. Characterization of nanoporous ABO layers was carried out through x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–visible (UV–Vis) diffuse reflectance spectroscopy and photoluminescence (PL). Effects of heat treatment on crystallinity, morphology and gas-sensing properties were investigated in detail. The XRD measurements showed that a gradual phase change from beta to gamma occurs with an increase in annealing temperature. The beta to gamma transformation occurred between 500 and 600 °C. The changes in the average crystallite sizes of beta and gamma occurring during heat treatment of the ABO layers are correlated with the mechanism of gamma-phase nucleation. During the growth of the gamma phase, the grain size gets enlarged with a reduction in the total area of grain boundary. The pores’ formation and the pore diameter of both anodized and annealed samples were found to be in the range of 50 to 150 nm. The band gap of the ABO layer crystallines was determined using the diffuse reflectance technique according to the Kubelka–Munk theory. Results showed that the band gap of the ABO layer decreased from 4.09 to 2.42 eV when the particle size decreased from 58 to 24 nm. The CO2 sensing properties of the ABO were investigated at room temperature for 0–100 ppm concentration. The variations in the electrical resistances were measured with the exposure of CO2 as a function of time. The maximum value of the response magnitude of 77% was obtained for 100 ppm of CO2. These experimental results show that the ABO layer of nanoporous is a promising material for CO2 sensors at room temperature.

High dynamic range infrared images detail enhancement based on local edge preserving filter

In the field of infrared (IR) image processing, displaying a high dynamic range (HDR) image on a low dynamic range display equipment with a natural visual effect, clear details on local areas and less artifacts is an important issue. In this paper, we present a new approach to display HDR IR images with contrast enhancement. First, the local edge-preserving filter (LEPF) is utilized to separate the image into a base layer and detail layer(s). After the filtering procedure, we use an adaptive Gamma transformation to adjust the gray distribution of the base layer, and stretch the detail layer based on a human visual effect principle. Then, we recombine the detail layer and base layer to obtain the enhance output. Finally, we adjust the luminance of output by applying multiple exposure fusion method. The experimental results demonstrate that our proposed method can provide a significant performance in terms of enhancing details and less artifacts than the state of the arts.

AN IHS-BASED ENHANCEMENT METHOD WITH IMPROVED SCALE/SHIFT PARAMETER OF LINEAR MODEL

Abstract. An IHS-based enhancement method for colour images (IEM) is presented in this paper. An improved gamma transformation was applied to enhance the brightness and texture details of colour images taken in dark conditions. Moreover, a spatial filter was used to prevent the loss of details of highlighted areas. The method was tested with the images from the database of Simon Fraser University (SFU) and from the Chinese ZIYUAN-02C satellite. The experimental results show our proposed method could effectively enhance the luminance and texture of the images, especially for those taken in dim conditions, and maintain the hue and saturation of original images.

AN IHS-BASED ENHANCEMENT METHOD WITH IMPROVED SCALE/SHIFT PARAMETER OF LINEAR MODEL

An IHS-based enhancement method for colour images (IEM) is presented in this paper. An improved gamma transformation was applied to enhance the brightness and texture details of colour images taken in dark conditions. Moreover, a spatial filter was used to prevent the loss of details of highlighted areas. The method was tested with the images from the database of Simon Fraser University (SFU) and from the Chinese ZIYUAN-02C satellite. The experimental results show our proposed method could effectively enhance the luminance and texture of the images, especially for those taken in dim conditions, and maintain the hue and saturation of original images.

Evaluation of various digital image processing techniques for detecting critical crescent moon and introducing CMD – A tool for critical crescent moon detection

Critical crescent moon detection is a new subject in astronomical image processing. Astronomers take photos with valuable astronomical calculations using CCD cameras and telescopes. Crescent moon might not be visible in such photos, so they must be enhanced. For this purpose, we apply common image processing methods on crescent moon images such as power operator, gamma transformation, global and local histogram equalization, POSHE, CLAHE, local enhancement, gain/offset correction, homomorphic filtering, SSR, MSR, MSRCR, wavelet and curvelet transformations. Second, we use our new methods like PB, POSP, HShistV, CurvHShistV and local brightness intensity enhancement to detect the crescent. Then we evaluate and compare the outputs of these algorithms by standard subjective evaluation tests. Finally, we conclude that these methods can give us enhanced images in which the crescent moon can be seen by human observers. We introduce our new toolbox which is named CMD, a standalone tool developed in Matlab for Critical Crescent Moon Detection using the above techniques.

Density Regression Based on Proportional Hazards Family

This paper develops a class of density regression models based on proportional hazards family, namely, Gamma transformation proportional hazard (Gt-PH) model . Exact inference for the regression parameters and hazard ratio is derived. These estimators enjoy some good properties such as unbiased estimation, which may not be shared by other inference methods such as maximum likelihood estimate (MLE). Generalised confidence interval and hypothesis testing for regression parameters are also provided. The method itself is easy to implement in practice. The regression method is also extended to Lasso-based variable selection.

A role of interfacial energy balance in delta to gamma transformation kinetics in carbon steel with dispersed second phase particles analyzed by phase-field simulation

It was reported in the authors’ previous study that second phase particles in δ phase induce a retardation effect on migration of δ–γ interface in carbon steels as is similar to the pinning effect on the grain growth in polycrystalline materials and effects of volume fraction and size of the particle were clarified. However, several other factors are expected to affect the magnitude of the retardation effect. In this study, the effect of the different interfacial energies is systematically investigated by means of two-dimensional phase-field simulations, and it is found that the magnitude of the retardation effect can be described by the parameter, Δσ=σPγ−σPδ where σPγ (σPδ) is the interfacial energy between the particle and γ (δ) phases. The large positive value of Δσ yields the strong pinning effect. In addition, it is shown that the δ–γ interface migration is accelerated when Δσ is large negative. These results originate from the increase in the total interfacial energy when Δσ>0 and the decrease when Δσ<0 during the interface passing through the particles. A degree of the retardation, Δa was summarized in the relation, Δa=m1(r/l2)(1+m2Δσ), where m1 and m2 are constants and r is radius of the particle and l is particle spacing.

감마변환을 사용한 히스토그램 평활화

Histogram equalization generally has the disadvantage that if the distribution of the gray level of an image is concentrated in one place, then the range of the gray level in the output image is excessively expanded, which then produces a visually unnatural result. However, a gamma transformation can reduce such unnatural appearances since it operates under a nonlinear regime. Therefore, this paper proposes a new histogram equalization method that can improve image quality by using a gamma transformation. The proposed method 1) derives the proper form of the gamma transformation by using the average brightness of the input image, 2) linearly combines the earlier gamma transformation with a CDF (Cumulative Distribution Function) for the image in order to obtain a new CDF, and 3) to finally perform histogram equalization by using the new CDF. The experimental results show that relative to existing methods, the proposed method provides good performance in terms of quantitative measures, such as entropy, UIQ, SSIM, etc., and it also naturally enhances the image quality in visual perspective as well.

Phase-Field Simulations and Analysis of Effect of Dispersed Particles on Migration of Delta to Gamma Transformation Interface

Retardation effect of dispersed inert particles on delta–gamma interface migration in carbon steels during isothermal delta to gamma transformation is analyzed by two-dimensional phase-field simulations. The effect is systematically investigated for different values of particle radius, r, particle spacing, l, and initial carbon concentration of delta phase. The retardation effect becomes stronger when the pinning parameter described by r/l 2 is larger and the carbon concentration of delta phase is higher, indicating that delta to gamma transformation kinetics can be retarded in a similar way to the pinning effect on grain growth kinetics.

Formation of Fine Clusters in High-Temperature Oxidation of Molten Aluminum

High-temperature oxidation of molten aluminum was investigated by high-resolution electron microscopes in order to determine the possibility of heterogeneous nucleation of aluminum grains on oxide for the grain refinement and structural uniformity of intensively melt-sheared aluminum alloys. High-resolution observations detect initial amorphous phase and gamma-alumina phase and show fine clusters with size of about 150 to 200 nm composed of extremely fine aluminum grains and gamma-alumina or amorphous aluminum oxide. Furthermore, high-resolution lattice images and diffraction patterns show no orientation relationship, although there is a specific orientation between gamma-alumina and aluminum along (111)[110] with high potency of heterogeneous nucleation. The volumetric shrinkage by the transformation of gamma- into alpha-alumina causes the surface oxide films to repeatedly rupture and leads to the creation of channels to the base melt surface for further oxidation of fresh metal. Based on the observations, the mechanism of high-temperature oxidation of molten aluminum and formation of the fine clusters as well as the possibility of the heterogeneous nucleation of aluminum grains are discussed.

基于数码相片Gamma校正的水稻叶面积指数估算

PDF HTML阅读 XML下载 导出引用 引用提醒 基于数码相片Gamma校正的水稻叶面积指数估算 DOI: 10.5846/stxb201211231660 作者: 作者单位: 南京信息工程大学, 气象灾害省部共建教育部重点实验室,南京信息工程大学 遥感学院,南京信息工程大学 遥感学院,南京晓庄学院 生物化工与环境工程学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点基础研究发展计划（2010CB950701）；国家自然科学基金（41071281）；江苏省高校优势学科建设工程资助项目 Estimation of paddy rice leaf area index based on photo gamma correction Author: Affiliation: Key Laboratory of Meteorlogical Disaster of Ministry of Education, Nanjing University of Information Science Technology,Nanjing University of Information Science Technology,Nanjing University of Information Science Technology,School of Bio-Chemical and Environmental Engineering,Nanjing Xiaozhuang University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:随着数码相机的日益普及，利用数码相机进行作物叶面积指数（LAI）测量不断得以应用。由于数码相机成像时会对入射光辐射强度进行Gamma编码变换，输出的相片DN（Digital Number）值与入射光辐射强度呈非线性关系，会造成在确定相片中植被叶片与背景的分割阈值时出现误差，并最终导致LAI估算存在较大不确定性。以水稻为研究对象，获取不同生长期水稻冠层相片并结合同步LAI 2000测量的LAI数据，基于相片Gamma校正原理，对水稻不同生长期冠层相片进行Gamma校正，在此基础上利用冠层孔隙率方法，估算不同生长期水稻LAI。结果表明，经过Gamma校正相片估算的水稻LAI总体精度有显著提高，相片估算的IMAGE LAI与LAI-2000测量值比较的决定系数达到0.71（P < 0.05）。在整个观测期内，两种方法观测的LAI值在时间变化趋势上表现一致，但在不同生长期内存在差别，在水稻分蘖期和拔节期相片估算的IMAGE LAI要高于LAI-2000测量值，孕穗期到抽穗期期间IMAGE LAI低于LAI-2000测量值，乳熟期到成熟期IMAGE LAI又高于LAI-2000的观测结果。 Abstract:The automatic compensation effect in a digital camera can cause a bias of the digital number (DN) of the acquired images. This study carried out DN correction using gamma transformation theory combined with a look-up table method. The DN of the acquired image generally bears a nonlinear relationship with the intensity of incident light, which is an inherent characteristic in common commercial digital cameras. The gamma method is a nonlinear operation used to code and decode luminance or tri-stimulus values in video or still image systems. It has been widely used in photography and video productions, but is rarely used in image processing and applications to vegetation parameter determination. The gamma transformation is mainly used to compensate for the properties of human vision by maximizing the use of the bits or bandwidth relative to the perception of light and color. If images are not gamma encoded, they allocate too many bits or too much bandwidth to the darker areas that humans cannot differentiate and too few bits to the brighter areas that humans are sensitive to, and would thus require more bits to maintain the same visual quality. Although the visual quality of RAW image is generally not very appropriate in commercial use, the RAW image is precisely required in the retrieval of vegetation parameters to obtain a better fit with field measurements. Apart from the gamma correction, for the various annual paddy rice conditions we used the vertical gap fraction to obtain the leaf area index (LAI), which we named image LAI, and compared with the field LAI from LAI-2000. The results indicated that the correlation coefficients after the correction procedure were remarkably similar with an R2 of 0.71 (P < 0.05), better than for the uncorrected retrieved figures. In the tilling and jointing stages, there was a close approximation between the vertical gap fraction derived LAI and field LAI, but in the booting and heading stages the differences become obvious, reaching a maximum of 0.38. However, in the milk-ripened and maturation stages, the reverse occurred; the field LAI was higher than the vertical gap fraction derived-LAI mainly because the foliage of the rice paddy went yellow. In general, there was a good fit between the retrieved LAI and field LAI, but the estimation accuracy varied depending on the phenology of paddy rice. A better fit between image LAI and LAI 2000 was observed in the tilling and jointing stages, when a larger bias between image LAI and field LAI was observed in the booting and heading stages, while an overestimation in image LAI was observed in the milk-ripened and maturation stages. The commercial digital camera can carry out easy and low cost research given its characteristic properties (ease of use, less costly, and lack of atmospheric effects). These features enable anyone to carry out good estimation work related to vegetation. These factors and many related articles make the digital camera a useful alternative method for assessing vegetation parameters such as vegetation fraction, leaf color, plant type and leaf area index. 参考文献 相似文献 引证文献

Boosting the stability of wavelet-based contrast enhancement of color images through gamma transformations

Contrast enhancement in color images can be problematic due to many causes as, e.g. generation of unnatural colors, inversion of the order between level lines of the three chromatic channels and so on. Since the human visual system automatically realizes an efficient local contrast enhancement, it is natural to take inspiration from its features to build models that improve contrast in digital color images. In recent years, it has been proven that it is possible to build a variational framework which serves as a unified home for color correction models which comply with the basic perceptual features of color perception. This framework was built in the spatial domain and then extended in the local frequency domain thanks to the use of wavelets. A noticeable characteristic of the wavelet perceptual color correction algorithm is the existence of a range of parameters for which its output images are artefact-free. In this paper we show how to boost the stability of this method through a suitable selection of a functional parameter.

A NOVEL METHOD OF COLOR IMAGE ENHANCEMENT BY COLOR SPACE TRANSFORMATION FOLLOWED BY GAMMA/LOGARITHMIC TRANSFORMATION

Visual enhancement of image plays a very important role in the field of medical imaging. Enhanced medical images are more suitable for analysis and proper diagnosis. We present a novel method of enhancement of color medical images in this paper. We are transforming color space of the image from RGB to HIS followed by application of logarithmic and gamma transformation on saturation and intensity component respectively. Hence we obtain a visually enhanced version of the original image. We have obtained excellent color medical image enhancement results presented in this paper.

Image Enhancement Algorithm Based on Zone System and Dual-Exposure Techniques

Luminance is crucially important to the quality of images. Colour, details, and texture can be washed out when luminance is exceedingly bright or hidden when luminance is overly dark. Logarithmic and gamma transformations are two well-known methods to alter exposure values. Unfortunately, both of these methods involve compressing the dynamic range of the image. This paper proposes a simple method based on the zone system devised for film photography to provide two levels of image compensation for the adjustment of luminance. The zone system is used to determine the level luminance, whereupon two compensation strategies are applied to produce an optimized high key or low key images. Experimental results demonstrate the superior performance of the proposed compensation method over existing methods, according to the evaluation using histograms, contour plots, the universal quality index, and structural similarity.

Nano-alumina by gel combustion, its thermal characterization and slurry-based coating on stainless steel surface

Gel combustion method was used to prepare nano-alumina from aluminum nitrate and stoichiometric amount of glycine as fuel. The TG–DTA pattern of the as-prepared powder (combustion product) exhibited exotherms with peaks around 500 and 900 °C accompanied with loss of weight of 25 and 5 % attributed to burning away of carbon left behind and decomposition of residual reaction intermediates left behind, respectively. Even though mass stability is attained above 900 °C, the DTA exhibited an exotherm around 1,150 °C attributed to transformation of gamma to alpha form of alumina. The XRD studies revealed that the powder heated to 900 °C was chemically pure nano-crystalline alumina while that heated above 1,150 °C was crystalline alpha form. As nano-crystalline powders are sinter-active, the nano-crystalline alumina formed by calcination at 900 °C was used to form the coating. A morphological feature of the agglomerates of nano-alumina powders were evaluated using SEM. The powder was de-agglomerated by wet grinding method. The dispersion conditions to form slurry using 900 °C calcined powder for slurry-based coating was optimized using zeta-potential studies, and it was found to exhibit a maximum value of −45 mV at a pH of 9. After 8 h of grinding, the median agglomerate size reduced to 2 μm. Rheological studies exhibited desired pseudoplastic behavior in the range of 10–20 vol.% of solid while the slurry with 15 vol.% only form crack free, dense, and adherent coating after heat treatment at 1,150 °C. The morphology of the coating was found to be uniform and dense.

Syndromic surveillance models using Web data: The case of scarlet fever in the UK

Recent research has shown the potential of Web queries as a source for syndromic surveillance, and existing studies show that these queries can be used as a basis for estimation and prediction of the development of a syndromic disease, such as influenza, using log linear (logit) statistical models. Two alternative models are applied to the relationship between cases and Web queries in this paper. We examine the applicability of using statistical methods to relate search engine queries with scarlet fever cases in the UK, taking advantage of tools to acquire the appropriate data from Google, and using an alternative statistical method based on gamma distributions. The results show that using logit models, the Pearson correlation factor between Web queries and the data obtained from the official agencies must be over 0.90, otherwise the prediction of the peak and the spread of the distributions gives significant deviations. In this paper, we describe the gamma distribution model and show that we can obtain better results in all cases using gamma transformations, and especially in those with a smaller correlation factor.

Phase transformations in an AISI 410S stainless steel observed in directional and laser-induced cooling regimes

The applications of the chromium ferritic stainless steel AISI 410S have been considerably increased in the last years in many technical fields as chemical industries and oil or gas transportation. However, the phase transformation temperatures are, currently, unknown for this alloy. The aim of this work is to determine the alpha to gamma transformation temperatures of the AISI 410S alloy in different cooling conditions and to analyze them using continuous cooling theory. In order to achieve different cooling rates and thermal conditions, two complementary techniques were used: Bridgman furnace crystal growth and laser remelting technique. The measured solidification temperature was around 1730 and 1750 K. Plate-like and dendritic austenite precipitates were obtained in solid-state phase using growth rates between 5 and 10 µm/s in directional growth experiments. Only plate-like austenite phase was observed in the experiments using growth rates above 100 µm/s. The appearance of dendrites, with the consequent segregation of the elements, can be previously determined by the microstructure modeling currently proposed. Massive austenite can be produced from 0.3 to 10 mm/s rates at temperatures between 1100-1300 K. The structure might be less sensitive to corrosion because this phase is produced without microsegregation.