As an effective feature extraction method, locality sensitive discriminant analysis (LSDA) utilizes the neighbor relationship of data to characterize the manifold structure of data and uses label information of data to adapt to classification tasks. However, the performance of LSDA is affected by outliers and the destruction of local structure. Aiming at solving the limitations of LSDA, a locality sensitive discriminant projection (LSDP) algorithm is proposed. LSDP minimizes the distance of intraclass neighbor samples to maintain local structure and minimizes the intraclass non-neighbor samples to increase the compactness of intraclass samples after projection. The problem of outliers is alleviated by increasing the compactness of intraclass samples in subspace. At the same time, we redefine the weights of interclass neighbor samples to maintain the neighbor relationship of different labels samples. Holding the local structure of interclass samples maintains the manifold structure of data. Experiments on face datasets demonstrate the effectiveness of the LSDP algorithm.
Environments have great influence on the development and propagation of flame during fire disaster. When the fire is under the exertion of air flow, the structure of flame is changed by the air flow. The effect results of air flow depend on its flow parameters, such as velocity and flux. The influence of air flow on fire is one of the important parts in fire dynamics research. Experiment study was conducted to study the structure change of a pool fire under air flows with fixed scale but different velocities. Flame temperature was measured by fine wire thermocouples in different positions of fire. Heat flux gauge was used to measure the change of heat flux. A pair of photoelectric probe measured the fluctuation of flame. The velocity of air flow was measured and all other test data were processed by wavelet transforms. Low frequency components corresponding to stable part of fire and high frequency component with corresponding to unstable part of fire are separated by wavelet analysis. The stable threshold that disappears under a certain velocity of air flow is illustrated by the data process. These results are also compared with those obtained from short time Fourier transforms.
Fine water mist can be used to restrain thermal hazard in some special situations, such as information center and telephone exchange center. A set of experiment was conducted to study the interaction of fine water mist with hot objects of different shape. An adjuster was designed to control the surface temperature of them avoiding over-heated. These objects were chosen to simulate the shape of cable and box used in electric equipment. Change of thermal field around these hot objects was measured before and after exertion of fine water mist. The flow procedure of fine water mist on the objects was displayed by an optical system. Vaporization height of fine water mist above different hot object was also measured. The restrain efficiency of fine water mist with different flux but same droplet size is compared. The experiment results serve as reference to engineering application of fine water mist to restrain thermal hazard of electric apparatus.
A set of experiment was conducted to study the initial shock wave, which is generated in early launching stage and harmful to human and equipment. Profile of pressure-time history consists of shock wave and rocket noise, which are the two inherent flow features of rocket exhaust flow. This makes it difficult to calculate the typical parameters such as peak overpressure, positive duration and waveform coefficient. Thus the intensity of shock wave is hard to determine by traditional methods. Wavelet threshold de-noise is used in this paper to detect shock wave profile from noise. Daubechies and Symlets wavelet families are compared in threshold treating of shock wave data. Wavelet threshold plus a priori knowledge makes the initial shock wave well detected from rocket noise. Three characteristic parameters of shock wave are determined and compared in the study. The results show that low order wavelet with small support width can keep singularity of shock wave better.This helps to understand the performence of initial shock wave of rocket jet in engineering application.
Wall plays an important role in building fire. It can be used to block the fire and prevent its propagation. It restricts free air entrainment, heat transfer and radiation from the wall side of fire. In other cases the wall will accelerate fire to spread to ceiling. Experiment research was carried out to study the influence of wall on the shape of flame and temperature distribution. An array of thermocouple is applied to study the temperature distribution along the wall. A large caliber laser Moiré Deflectometry was used to display the flow procedure during the interaction of wall and flame, especially the changing of buoyant plum along the wall. Five cases, in which the plain wall was settled at 0, 5, 10, -5, and -10 degree with the axis of flame respectively, were studied. The distance between wall and flame was also changed in these five cases. The inclination effect of wall exerting on flame was clearly displayed. Influence of wall on the flame persistent zone height is calculated from experiment data in each case.
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