Current Issue : October - December Volume : 2014 Issue Number : 4 Articles : 6 Articles
Small aperture microphone arrays provide many advantages for portable devices and hearing aid equipment. In this paper, a\nsubspace based localization method is proposed for acoustic source using small aperture arrays. The effects of array aperture\non localization are analyzed by using array response (array manifold). Besides array aperture, the frequency of acoustic source\nand the variance of signal power are simulated to demonstrate how to optimize localization performance, which is carried out by\nintroducing frequency error with the proposed method. The proposed method for 5mm array aperture is validated by simulations\nand experiments with MEMS microphone arrays. Different types of acoustic sources can be localized with the highest precision\nof 6 degrees even in the presence of wind noise and other noises. Furthermore, the proposed method reduces the computational\ncomplexity compared with other methods....
Wireless sensor network (WSN) has become one of the most promising network technologies for many useful applications.\nHowever, for the lack of resources, it is different but important to ensure the security of the WSNs. Key management is a corner\nstone on which to build secure WSNs for it has a fundamental role in confidentiality, authentication, and so on. Combinatorial\ndesign theory has been used to generate good-designed key rings for each sensor node inWSNs. A large number of combinatorial\ndesign based key management schemes have been proposed but none of them have taken key updating into consideration. In this\npaper, we point out the essence of key updating for the unital design based keymanagement scheme and propose two key updating\nmethods; then, we conduct performance analysis on the two methods from three aspects; at last, we generalize the two methods to\nother combinatorial design based key management schemes and enhance the second method....
Cyber physical systems have grown exponentially and have been attracting a lot of attention over the last few years. To retrieve and\nmine the useful information from massive amounts of sensor data streams with spatial, temporal, and other multidimensional\ninformation has become an active research area. Moreover, recent research has shown that clusters of streams change with a\ncomprehensive spatial-temporal viewpoint in real applications. In this paper, we propose a spatial-temporal clustering algorithm\n(STClu) based on nonnegativematrix trifactorization by utilizing time-series observational data streams and geospatial relationship\nfor clusteringmultiple sensor data streams. Instead of directly clusteringmultiple data streams periodically, STClu incorporates the\nspatial relationship between two sensors in proximity and integrates the historical information into consideration. Furthermore,\nwe develop an iterative updating optimization algorithm STClu. The effectiveness and efficiency of the algorithm STClu are both\ndemonstrated in experiments on real and synthetic data sets. The results show that the proposed STClu algorithm outperforms\nexisting methods for clustering sensor data streams....
Vehicle sensor to detect rain drop on and above waveguide utilizing light deflection and scattering was realized, keeping wide\nsensing coverage and sensitivity to detect mist accumulation. Proposed sensor structure under stacked light wave guide consisted\nof light blocking fixture surrounding photodetector and adjacent light source. Tilted air gap between stacked light waveguide and\nlight blocking fixture played major role to increase sensitivity and to enhance linearity. This sensor structure eliminated complex\ncollimating optics, while keeping wide sensing coverage using simple geometry. Detection algorithm based on time-to-intensity\ntransformation process was used to convert raining intensity into countable raining process. Experimental result inside simulated\nrain chamber showed distinct different response between light rain and normal rain. Application as automobile rain sensor is\nexpected....
The connecting of things to the Internet makes it possible for smart things to access all kinds of Web services. However, smart\nthings are energy-limited, and suitable selection of Web services will consume less resources. In this paper, we study the problem\nof selecting someWeb service from the candidate set.We formulate this selection ofWeb services for smart things as single-source\nmany-target shortest path problem. We design algorithms based on the Dijkstra and breadth-first search algorithms, propose an\nefficient pruning algorithm for breadth-first search, and analyze their performance of number of iterations and I/O cost. Our\nempirical evaluation on real-life graphs shows that our pruning algorithm is more efficient than the breadth-first search algorithm....
Two-channel metal detector, having two sets of perpendicularly oriented sensor antennas, is proposed to expand detectable size,\nranging from mm through cm scale, of metal sensor, while conventional metal sensor is dedicated for detection only in mm or\ncm scale. The characteristics of the two metal detection sensor channels were investigated, respectively, and the interference effect,\nwhile in simultaneous operation, between two sensor channels was discussed. Metal detection channel, having sensitivity in mm\nscale, showed detectable sensitivity to moving ferrous sphere, with diameter down to 0.7 mm, at 50 kHz exciting frequency and\nenhanced sensitivity distribution. And metal detection channel having sensitivity in cm scale showed more uniform sensitivity\ndistribution with the flexibility for future modular construction. The effect of interference, while in simultaneous operation of two\nsensors, resulted in reduced output response, but still within usable detection range. Thus it was feasible to operate two sensors,\nhaving different sensitivity range, simultaneously and to extend detection range frommmto cm scale, within practically acceptable\ninterference....
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