In cognitive radio network, considering that secondary user (SU) packets waiting in the cache will stop waiting and exit the system because of impatience, a dynamic stop-adjustable control mechanism is proposed in a s...
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In this paper, a compact and highly selective stacked filtering dense dielectric patch (DDP) antenna (DDPA) is proposed. By placing a pair of thin DDP with high dielectric constant along the y axis on the DDP with low...
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In cognitive radio network, considering that secondary user (SU) packets waiting in the cache will stop waiting and exit the system because of impatience, a dynamic stop-adjustable control mechanism is proposed in a s...
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ISBN:
(数字)9798331506230
ISBN:
(纸本)9798331506247
In cognitive radio network, considering that secondary user (SU) packets waiting in the cache will stop waiting and exit the system because of impatience, a dynamic stop-adjustable control mechanism is proposed in a single-channel network environment where impatient SU packets leave the system in advance. The SU packets in the cache are divided into retry SU packets and newly arrived SU packets, assuming that only the newly arrived SU packets can stop and leave the system because of impatience. A discrete-time queueing model is established, a three-dimensional Markov chain is constructed, and SU packets’ performance indicators are derived. Numerical experiments are carried out to verify the validity of the presented stop-adjustable control strategy. By comparing with the stopadjustable control mechanism for unclassified SU packets, it is found that the proposed stop-adjustable control mechanism for classified SU packets can effectively improve SU packets’ performance.
To solve the problems of poor denoising effect and limited threshold accuracy in traditional Canny algorithm, an improved Canny algorithm is proposed in this paper. Firstly, an image preprocessing method based on hybr...
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ISBN:
(数字)9798350350210
ISBN:
(纸本)9798350350227
To solve the problems of poor denoising effect and limited threshold accuracy in traditional Canny algorithm, an improved Canny algorithm is proposed in this paper. Firstly, an image preprocessing method based on hybrid filtering is developed. On the basis of Gaussian filtering, the adaptive median filtering is adopted to denoise the image, and homomorphic filtering is used to enhance the high frequency information of image in the frequency domain. Besides, Sobel operator is used instead of Roberts operator to calculate the gradient amplitude and direction of the image. Finally, an iterative threshold selection method combining MEM and Otsu is proposed. After obtaining the high and low thresholds by MEM and Otsu respectively, the optimal threshold is calculated using iterative algorithm, which can improve the accuracy and adaptability of threshold. It is proved that the proposed algorithm can preserve the image details while ensuring the denoising effect, and the detected edges have better connectivity and smoothness.
In this paper, a compact and highly selective stacked filtering dense dielectric patch (DDP) antenna (DDPA) is proposed. By placing a pair of thin DDP with high dielectric constant along the y axis on the DDP with low...
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ISBN:
(数字)9798350363609
ISBN:
(纸本)9798350363616
In this paper, a compact and highly selective stacked filtering dense dielectric patch (DDP) antenna (DDPA) is proposed. By placing a pair of thin DDP with high dielectric constant along the y axis on the DDP with low dielectric constant, the resonant frequency of the TE 12 mode is adjusted to approach low frequency and form a passband with the TE 11 mode. By loading a U-shaped microstrip feeding line on the microstrip feeding line, the bandwidth can be further broadened and the TE 11 , TE 11 + δ and TE 12 modes can be successfully excited in the passband. The radiation nulls are generated by the U-shaped microstrip line and non-radiative TE 12 mode, respectively. By adjusting the length of the U-shaped microstrip line and the size of DDP with high dielectric constant, the independent adjustment of radiation nulls can be achieved. Finally, the proposed filtering antenna achieves a relative bandwidth of 11.66 % (4.04-4.54 GHz). The average realized gain and peak gain are 6.89 dBi and 7.1 dBi, respectively. The realized gain in the passband is very flat, and the fluctuation is less than 0.7 dBi. The proposed antenna has the advantages of compactness, high selectivity and flat gain, and it can be applied to modern satellite communication and wireless communication systems.
Image segmentation aims to partition an image according to the objects in the scene and is a fundamental step in analysing very high spatial-resolution (VHR) remote sensing imagery. Current methods struggle to effecti...
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