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Abstract
In this paper an edge detection algorithm based on wavelet transform with Gaussian filter was proposed. In this algorithm original images are firstly converted into gray images and then each pixel was analyzed using wavelet transform to find the local maximum of the gray gradient of each pixel along the phase angle direction and compared with a given threshold value, through which real edge can be kept and fake ones will be eliminated. In the computation of local maximum, the gray gradients computed in eight directions, which can improve precision of edge detection. After the investigation of influence of filter length, scale and threshold value on the edge detection and validation by comparison with N.L. Fenandez-Garcia's Minimean and Minimax methods for 100 real color images, we applied this algorithm to bubbly gas-liquid two-phase flow. Compared with Canny operator, present result is more close to real bubble shape and can distinguish very close bubbles, which indicates the algorithm is effective and can be used to study the interaction between different phases and flow field in multiphase flow.
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Edges are important cues defining coherent auditory objects. As a model of auditory edges, sound on- and offset are particularly suitable to study their neural underpinnings because they contrast a specific physical input against no physical input. Change from silence to sound, that is onset, has extensively been studied and elicits transient neural responses bilaterally in auditory cortex. However, neural activity associated with sound onset is not only related to edge detection but also to novel afferent inputs. Edges at the change from sound to silence, that is offset, are not confounded by novel physical input and thus allow to examine neural activity associated with sound edges per se. In the first experiment, we used silent acquisition functional magnetic resonance imaging and found that the offset of pulsed sound activates planum temporale, superior temporal sulcus and planum polare of the right hemisphere. In the planum temporale and the superior temporal sulcus, offset response amplitudes were related to the pulse repetition rate of the preceding stimulation. In the second experiment, we found that these offset-responsive regions were also activated by single sound pulses, onset of sound pulse sequences and single sound pulse omissions within sound pulse sequences. However, they were not active during sustained sound presentation. Thus, our data show that circumscribed areas in right temporal cortex are specifically involved in identifying auditory edges. This operation is crucial for translating acoustic signal time series into coherent auditory objects.
The reactor in three-phase fluidized bed is a close reaction device, which contact area is greatly, has high production efficiency, and has a wide-ranging application in the reactions such as mineral oil hydrogenization splitting and so on. The air bubble sizes and the distributing with the moving velocity upward in the fluidized bed, will decided the effective passing area and the reaction efficiency. The image identifying and analyzing system, by means of gray degree values, can be used to identified and analyzed the air bubbles state in the reactor, such as the distributing, the moving, the gathering and blowing out of the air bubbles.
This paper introduces some applications in image processing with wavelets, such as edge detection, pattern recognition and image segmentation. Edge detection includes contour extraction and background removal for an illustration of gray - level, extraction of tumor region in color image and enlargement of type size of Chinese character. As for recognition of Chinese character or character at first, we can reduce the dimensionality of two dimensional patterns to one dimensional sign, then do wavelets decomposition for these one dimensional patterns, at last compute fractal dimension of each sub - pattern, so feature vectors can be obtained and used to recognition. The characters after affine transformation can also be recognized by a dyadic wavelet affine invariant function. At last we introduce two means of image segmentation. One is based on energy analysis, another is singularity analysis.
A method is described for transmitting digitalized video signals to reduce channel capacity from that needed for standard PCM. This method takes advantage of the inability of the human eye to notice the exact amplitude and shape of short brightness transients. The transmitted information consists of the amplitudes and times of occurrence of the “edge” points of video signals. These selected samples are coarsely quantized if they belong to high-frequency regions, and the receiver then interpolates straight lines between the samples. The system was simulated on the IBM 704 computer. The processed pictures and obtained channel-capacity savings are presented.
Whole field velocity and point temperature and surface heat flux measurements were performed to characterise the interaction of a single rising ellipsoidal air bubble with the free convection flow from a heated flat surface immersed in water at different angles of inclination. Two thermocouples and a hot film sensor were used to characterise heat transfer from the surface, while a time-resolved digital particle image velocimetry technique was used to map the bubble induced flow in a plane parallel to the surface. Heat flux fluctuations, preceding and following the bubble passage, were shown to correlate with the variation in both local flow velocities and fluid temperatures. The largest increases in heat transfer were recorded when both flow and temperature effects combined to enhance the convective cooling simultaneously. Such conditions were shown to be most likely met when the block was inclined at 45°, thus forcing the bubble to slide closer to the heated surface and hence to the thermal boundary layer.
This research uses the object extracting technique to extract – the thumb, index, middle, ring, and small fingers from the hand images. The algorithm developed in this research can find the precise locations of the fingertips and the finger-to-finger-valleys. The extracted fingers contain many useful geometry features. One can use these features to do the person identification. The orientations of the index, middle and ring fingers are found in this research. Image rotating, image shifting, and image interpolating techniques are used to align different persons’ fingers. Image subtraction is used to exam the difference of two fingers.
To establish reasonable safety concepts for the realization of commercial liquid-metal fast breeder reactors, it is indispensable to demonstrate that the release of excessive energy due to re-criticality of molten core could be prevented even if a severe core damage accident took place. Two-phase flow due to the boiling of fuel-steel mixture in the molten core pool has a larger liquid-to-gas density ratio and higher surface tension in comparison with those of ordinary two-phase flows such as air-water flow. In this study, to investigate the effect of the recirculation flow on the bubble behavior, visualization and measurement of nitrogen gas-molten lead bismuth in a rectangular tank was performed by using neutron radiography and particle image velocimetry techniques. Measured flow parameters include flow regime, two-dimensional void distribution, and liquid velocity field in the tank. The present technique is applicable to the measurement of velocity fields and void fraction, and the basic characteristics of gas-liquid metal two-phase mixture were clarified.
In this study, an on-line concentration method which coupled cation-selective exhaustive injection (CSEI) sweeping technology with microemulsion electrokinetic chromatography (MEEKC) was used to detect and analyze several tobacco alkaloids (nornicotine, anabasine, anatabine, nicotine, myosmine and cotinine) that are commonly found in various tobacco products. First, the effects of microemulsion compositions (oil, cosurfactant and solution pH) were examined in order to optimize the alkaloid separations in conventional MEEKC. The pH value and the injection length of basic plug were found to be the predominant influences on the alkaloid stacking. This optimal CSEI sweeping MEEKC method provided approximately 180- to 540-fold increase in detection sensitivity in terms of peak height without any loss in separation efficiency when compared to normal MEEKC separation. Furthermore, this proposed CSEI sweeping MEEKC method was applied successfully for the detection of the minor alkaloids nornicotine, anabasine and anatabine in tobacco products.