Current Issue : July - September Volume : 2014 Issue Number : 3 Articles : 5 Articles
We present a methodology and a circuit to extract liquid resistance and capacitance simultaneously from the same output signal\nusing interdigitated sensing electrodes. The principle consists in the generation of a current square wave and its application to the\nsensor to create a triangular output voltage which contains both the conductivity and permittivity parameters in a single periodic\nsegment. This concept extends the Triangular Waveform Voltage (TWV) signal generation technique and is implemented by a\nsystem which consists in a closed-loop current-controlled oscillator and only requires DC power to operate. The system interface\nis portable and only a small number of electrical components are used to generate the expected signal. Conductivities of saline\nNaCl and KCl solutions, being first calibrated by commercial equipment, are characterized by a system prototype. The results show\nexcellent linearity and prove the repeatability of the measurements. Experiments on water-glycerol mixtures validate the proposed\nsensing approach to measure the permittivity and the conductivity simultaneously. We discussed and identified the sources of\nmeasurement errors as circuit parasitic capacitances, switching clock feedthrough, charge injection, bandwidth, and control-current\nquality....
We investigate the properties of data collection in wireless sensor networks, in terms of both capacity and power allocation strategy.\nWe consider a scenario in which a number of sensors observe a target being estimated at fusion center (FC) using minimum meansquare\nerror (MMSE) estimator. Based on the relationship between mutual information and MMSE (I-MMSE), the capacity of\ndata collection in coherent and orthogonal multiple access channel (MAC) models is derived. Considering power constraint, the\ncapacity is derived under two scenarios: equal power allocation and optimal power allocation of bothmodels.We provide the upper\nbound of capacity as a benchmark. In particular, we show that the capacity of data collection scales as T((1/2)log(1 + ??)) when the\nnumber of sensors L grows to infinity. We show through simulation results that for both coherent and orthogonal MAC models,\nthe capacity of the optimal power is larger than that of the equal power.We also show that the capacity of coherent MAC is larger\nthan that of orthogonal MAC, particularly when the number of sensors L is large and the total power P is fixed....
Affected by external noise and various nature disturbances,Wheel Force Transducer (WFT) signal may be completely submerged,\nand the sensitivity and the reliability of measurement can be strongly decreased. In this paper, a new wavelet packet denoising\nmethod based on sparse representation is proposed to remove the noises from WFT signal. In this method, the problem of\nrecovering the noiseless signal is converted into an optimization problem of recovering the sparsity of their wavelet package\ncoefficients, and the wavelet package coefficients of the noiseless signals can be obtained by the augmented Lagrange optimization\nmethod. Then the denoised WFT signal can be reconstructed by wavelet packet reconstruction. The experiments on simulation\nsignal and WFT signal show that the proposed denoising method based on sparse representation is more effective for denoising\nWFT signal than the soft and hard threshold denoising methods....
According to the report ââ?¬Å?GlobalHealth Risks of 2004ââ?¬Â issued byWHO(WorldHealth Organization) in Geneva 2009 (WHO, 2012),\nthe mortality rate of the diseases and cause of death which results from the smoke produced by burning solid fuel is ranked tenth,\noccupying 3.3% of the global amounts, and the DALYs (Disability Adjusted Life Years) is ranked the ninth, occupying 2.7% of the\nworld. Once the pollution occurred in an insufficient ventilation location, the womankind and children will be the most directly\naffected; therefore, we hoped to focus the measurement environment on indoor surroundings in this paper. This paper proposes a\npointing at several kinds of indoor pollutants and integrating multigas sensors, which includes carbon monoxide, carbon dioxide\ntotal volatile organic compounds, and so forth. Our paper combines gas sensors with WSN (Wireless Sensor Networks) nodes;\nwe provide users with optional monitoring subjects for constructing and also adapt ZigBee andWi-Fi modules to get united with\nuploading real-time sensor messages. Moreover, for the reason of decreasing installation cost of sensors and setting up easily, this\npaper builds a cloud data-viewing platformadditionally, enabling users to observe air quality through the cloud server everywhere....
We address the problem of formal and automated security verification of transport protocols for wireless sensor networks (WSN)\nthat may perform cryptographic operations. The verification of this class of protocols is difficult because they typically consist\nof complex behavioral characteristics, such as real-time, probabilistic, and cryptographic operations. To solve this problem, we\npropose a probabilistic timed calculus for cryptographic protocols and demonstrate how to use this formal language for proving\nsecurity or vulnerability of protocols. The main advantage of the proposed language is that it supports an expressive syntax and\nsemantics, allowing for studying real-time, probabilistic, and cryptographic issues at the same time. Hence, it can be used to verify\nsystems that involve these three properties in a convenient way. In addition, we propose an automatic verification method, based\non the well-known PAT process analysis toolkit, for this class of protocols. For demonstration purposes, we apply the proposed\nmanual and automatic proof methods for verifying the security of DTSN and SDTP, which are two of the recently proposedWSN\ntransport protocols....
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