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Remote sensing image classification based on sample incremental learning
Xue LI, Guangle YAO, Honghui WANG, Jun LI, Haoran ZHOU, Shaoze YE
Journal of Computer Applications    2024, 44 (3): 732-736.   DOI: 10.11772/j.issn.1001-9081.2023030366
Abstract265)   HTML10)    PDF (1266KB)(178)       Save

Deep learning models have achieved remarkable results in remote sensing image classification. With the continuous collection of new remote sensing images, when the remote sensing image classification models based on deep learning train new data to learn new knowledge, their recognition performance of old data will decline, that is, old knowledge forgetting. In order to help remote sensing image classification model consolidate old knowledge and learn new knowledge, a remote sensing image classification model based on sample incremental learning, namely ICLKM (Incremental Collaborative Learning Knowledge Model) was proposed. The model consisted of two knowledge networks. The first network mitigated knowledge forgetting by retaining the output of the old model through knowledge distillation. The second network took the output of new data as the learning objective of the first network and effectively learned new knowledge by maintaining the consistency of the dual network models. Finally, two networks learned together to generate more accurate model through knowledge collaboration strategy. Experimental results on two remote sensing datasets NWPU-RESISC45 and AID show that, ICLKM has the accuracy improved by 3.53 and 6.70 percentage points respectively compared with FT (Fine-Tuning) method. It can be seen that ICLKM can effectively solve the knowledge forgetting problem of remote sensing image classification and continuously improve the recognition accuracy of known remote sensing images.

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Optimized bit allocation algorithm for coding tree unit level
Xu YANG, Hongwei GUO, Wanxue LI
Journal of Computer Applications    2023, 43 (10): 3195-3201.   DOI: 10.11772/j.issn.1001-9081.2022091410
Abstract176)   HTML9)    PDF (742KB)(77)       Save

It the rate control algorithms of the new generation video coding standard H.266/VVC (Versatile Video Coding), the rate-distortion optimization technique with independent coding parameters is adopted. However, the Coding Tree Units (CTUs) within the same frame affect others in the spatial domain, and there are global coding parameters. At the same time, in the CTU-level bit allocation formulas, approximated coding parameters for bit allocation are used, resulting in the reduction of rate control accuracy and coding performance. To address these issues, a spatial-domain global optimization algorithm for CTU-level bit allocation called RTE_RC (Rate Control with Recursive Taylor Expansion) was proposed, and the global coding parameters were approximated by using a recursive algorithm. Firstly, a globally optimized bit allocation model in spatial-domain was established. Secondly, a recursive algorithm was used to calculate the global Lagrange multiplier in the CTU-level bit allocation formula. Finally, the bit allocation of coding units was optimized and the coding units were coded. Experimental results show that under the Low-Delay Prediction frame (LDP) configuration, compared with the rate control algorithm VTM_RC (Rate Control algorithm Versatile Test Model), the proposed algorithm has the rate control error decreased from 0.46% to 0.02%, the bit-rate saved by 2.48 percentage points, and the coding time reduced by 3.52%. Therefore, the rate control accuracy and rate distortion performance are significantly improved by the proposed algorithm.

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New power control scheme with maximum energy efficiency in wireless transmission
ZHAO Hui ZHANG Xue LIU Ming GONG Haigang WU Yue
Journal of Computer Applications    2013, 33 (02): 365-381.   DOI: 10.3724/SP.J.1087.2013.00365
Abstract824)      PDF (735KB)(386)       Save
Energy efficiency is an important metric in wireless Ad Hoc networks. Until now, there is no universally accepted definition of energy efficiency, and the related results are asymptotic or qualitative, which has limited its applicability. By regarding a bit as a physical particle with one unit of mass, the authors assumed that a bit in transmission possessed a certain amount of kinetic information energy. As a result, the energy efficiency of wireless transmission was defined as the ratio of information energy to physical energy. A quantitative analysis on energy efficiency in wireless transmission was carried out and meaningful results were obtained. It is concluded that the energy efficiency changes non-monotonously with the transmission power, and there is an optimal transmission power, with which the maximum energy efficiency will be acquired. The optimal transmission power was given to help the protocol design. Based on the theoretical results, a practical solution for transmission power control was proposed, and an extensive experimental study of it was given on the CC2420 radio. The results show the effectiveness of the proposed transmission power control scheme.
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Anti-jamming performance of frequency-hopping based on LDPC code
Ming-hao XUE Lin-hua MA Zhi-guo LIN Xiao-dong YE
Journal of Computer Applications    2011, 31 (08): 2037-2039.   DOI: 10.3724/SP.J.1087.2011.02037
Abstract1522)      PDF (438KB)(878)       Save
Frequency-hopping communication was combined with the Low-Density Parity-Check (LDPC) code to improve anti-jamming performance of frequency hopping communications. By simplifying the complexity of coding algorithm in the “greedy algorithm”, an offset layered quantization decoding called Layered Belief Propagation-Offset Min-Sum (LBP-OMS) algorithm was applied to improve the performance of error correction code words. The simulation results show that when certain frequency bands are covered by strong noise, the anti-interference ability of broadband frequency-hopping communications is improved by using the improved channel coding method.
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AES and its software implementation based on ARM920T
BAI Ru-xue LIU Hong-yan ZHANG Xin-he
Journal of Computer Applications    2011, 31 (05): 1295-1297.   DOI: 10.3724/SP.J.1087.2011.01295
Abstract1363)      PDF (553KB)(865)       Save
To improve the efficiency of Advanced Encryption Standard (AES) algorithm on ARM processor, an optimization of AES was introduced and realized on ARM920T processor. One-time key expansion was adopted. In the algorithm, SubBytes() and MixColumns() were defined as T-table to store, which could increase the speed. The proposed algorithm programmed by C language was simulated and debugged on the ARM Develop v1.2 platform. Different implementations were compared in storage space and processing speed and a variety of different key length algorithm performances were given. The experimental results show that the execution speed of the presented algorithm improves significantly.
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Quick algorithm for reconstructing line object adjacency relations
Ming-Xue LIAO Zhi-Hua FAN Xiao-Xin He
Journal of Computer Applications   
Abstract1356)      PDF (440KB)(970)       Save
Based on known coordinates of lines, the time complexity of usual algorithm for reconstructing adjacency relation among n line objects usually is O(n*n); in theory, its optimal value is at least O(C) and C is the cardinal number of adjacency relation. Based on hashed-bucket sorting, a quick algorithm with O(n(1+1/r)) average time complexity and with O(n) space complexity was given to reconstruct adjacency relation where r was the ratio of number of buckets used in the algorithm to n. It was proved that the problem can not be solved by sorting algorithm without extra space. With necessary extra space, a two-pass sorting algorithm with O[n(lb n+1+2/r)] time complexity, was also given. Applications show that the performance of the quick algorithm is over about 1~3 orders of magnitude higher than that of the usual algorithm.
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Study on architecture of WebGIS based on SOA
FeiXue Li
Journal of Computer Applications   
Abstract2115)      PDF (837KB)(889)       Save
SOA(Service-Oriented Architecture) is an architecture of software design suitable for changing environment, in which the difficulty in the sharing of data and operations can be removed to a certain extent. Conceptual framework, hierarchical relations, implementing framework and service implementing modes of WebGIS architecture based on SOA were designed. As a case study, a land use planning management information system for Yubei district, Chongqing city was implemented through XML-based Web service technology. The feasibility and validity of the architecture has been verified preliminarily.
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