Measuring perceptual contrast in digital images

In this paper we present a novel method to measure perceptual contrast in digital images. We start from a previous measure of contrast developed by Rizzi et al. [26], which presents a multilevel analysis. In the first part of the work the study is aimed mainly at investigating the contribution of the chromatic channels and whether a more complex neighborhood calculation can improve this previous measure of contrast. Following this, we analyze in detail the contribution of each level developing a weighted multilevel framework. Finally, we perform an investigation of Regions-of-Interest in combination with our measure of contrast. In order to evaluate the performance of our approach, we have carried out a psychophysical experiment in a controlled environment and performed extensive statistical tests. Results show an improvement in correlation between measured contrast and observers perceived contrast when the variance of the three color channels separately is used as weighting parameters for local contrast maps. Using Regions-of-Interest as weighting maps does not improve the ability of contrast measures to predict perceived contrast in digital images. This suggests that Regions-of-Interest cannot be used to improve contrast measures, as contrast is an intrinsic factor and it is judged by the global impression of the image. This indicates that further work on contrast measures should account for the global impression of the image while preserving the local information.     

Spatial pooling for measuring color printing quality attributes

Many objective image quality assessment algorithms firstly apply quality metrics in local regions that results in a quality map, and then pool the quality values in the quality map into a single quality score. The simplest pooling method is the average of quality values, which assumes that all the quality values are independent and equally important. However, visual perception is so complex that the assumption underlying average pooling might be too strict. There is an agreement that some regions in the images might be more perceptually significant, which leads to more advanced spatial pooling methods. In this work we evaluate existing spatial pooling methods for five important quality attributes, which are proposed to reduce the complexity of image quality assessment. The results show that: (1) more advanced spatial pooling methods are generally better than simple average; (2) spatial pooling depends on both image quality metrics and the attributes of the image.     

Information content of the near field: three-dimensional samples

We present an analysis of the accuracy and information content of three-dimensional reconstructions of the dielectric susceptibility of a sample from noisy, near-field holographic measurements, such as those made in scanning probe microscopy. Holographic measurements are related to the dielectric susceptibility via a linear operator within the accuracy of the first Born approximation. The maximum-likelihood reconstruction of the dielectric susceptibility is expressed as a linear combination of basis functions determined by singular value decomposition of the weighted measurement operator. Maximum a posteriori estimates based on prior information are also discussed. Semianalytical expressions are given for the likely error due to measurement noise in the basis function coefficients, resulting in effective resolution limits in all three dimensions. These results are illustrated by numerical examples.     

Characterization of properties of oriented strand boards from beech and poplar

The aim of this study was to evaluate the possibility of using European beech and poplar species to manufacture oriented strand boards (OSB). Beech and poplar strands with three different combinations of face/core ratios at densities of 650 and 720 kg/m³ were examined. Poly methylene diphenyl diisocyanate glue at 5 % was used with press conditions of 180 °C and 240 s. Findings showed that with increasing density the physical and mechanical properties of the different OSB combinations generally improved. Panels made of 60 % beech in face layers showed higher modulus of rupture and modulus of elasticity. Internal bond strength rose as the amount of beech strands in the core layer increased. Panels with 75 % beech strands in the core layer showed the maximum internal bond strength at 720 kg/m³. It was also observed that increasing the amount of beech in the core layer from 40 to 75 % decreased thickness swelling at both densities.     

Photoinduced electron transfer reactions: from the elucidation of old problems in bulk solutions towards the exploration of interfaces

The activities of our research group in the field of photoinduced electron transfer reactions are discussed and illustrated by several examples.     

ENGINEERING ASPECTS OF PENICILLIN G TRANSFER AND CONVERSION TO 6-AMINOPENICILLANIC ACID IN A BIOREACTOR WITH A MOBILE BED OF IMMOBILIZED PENICILLIN AMIDASE

This article presents studies on the external and internal mass transfers of penicillin G for 6-aminopenicillanic acid enzymatic production using a bioreactor with a stirred bed of immobilized penicillin amidase. By means of the substrate mass balance for a single particle of biocatalyst and considering the kinetic model adapted for competitive and noncompetitive inhibitions, specific mathematical models were developed for describing the profiles of penicillin G concentration in the outer and inner regions of biocatalyst and for estimating its mass flows in the liquid boundary layer surrounding the particle and inside the particle. The values of the mass flows are significantly influenced by the internal diffusion velocity and rate of the enzymatic conversion of substrate. These cumulated influences led to the appearance of an enzymatic inactive region near the particle center, its magnitude varying from 0 to 9.2% of the overall volume of particles.     

基于知网的词语语义相似度改进算法研究

词语语义相似度计算在很多自然语言处理相关领域都有着广泛应用.基于知网的现有词语语义相似度计算方法未深入考虑同棵义原层次树的义原距离、义原深度、义原密度及主次关系的影响,致使相似度计算结果并不够精确.针对该问题,提出一种词语语义相似度改进算法,通过分析知网中的义项表达式和义原层次树,用集合的加权平均值代替了义项相似度最大...     

Spectroscopic Studies of Model Photo-Receptors: Validation of a Nanosecond Time-Resolved Micro-Spectrophotometer Design Using Photoactive Yellow Protein and α-Phycoerythrocyanin

Time-resolved spectroscopic experiments have been performed with protein in solution and in crystalline form using a newly designed microspectrophotometer. The time-resolution of these experiments can be as good as two nanoseconds (ns), which is the minimal response time of the image intensifier used. With the current setup, the effective time-resolution is about seven ns, determined mainly by the pulse duration of the nanosecond laser. The amount of protein required is small, on the order of 100 nanograms. Bleaching, which is an undesirable effect common to photoreceptor proteins, is minimized by using a millisecond shutter to avoid extensive exposure to the probing light. We investigate two model photoreceptors, photoactive yellow protein (PYP), and α-phycoerythrocyanin (α-PEC), on different time scales and at different temperatures. Relaxation times obtained from kinetic time-series of difference absorption spectra collected from PYP are consistent with previous results. The comparison with these results validates the capability of this spectrophotometer to deliver high quality time-resolved absorption spectra.