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一、当前摩托车发动机质量性能存在的问题 业内权威人士承认,20多年以来,我国摩托车发动机的质量性能几无改进,更没有达到原装进口发动机的水平,我们过去进行的所谓创新,对改善提高发动机质量性能并无多大的实际意义.混合气燃烧不充分、油耗高、排放超标、动力不足、发动机温度过高、振动和噪声大、性能一致性和耐久性差、发动机通气管串机油、CG发动机发冲、大排量发动机优化设计开发等技术难题没突破等问题成为摩托车的通病. 相似文献
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光纤Bragg光栅的理论分析与研究 总被引:1,自引:0,他引:1
用耦合模理论导出了分析任意调制制折射率和任意chirp周期的光栅的简单公式,利用利于进行计算机模拟,并对国内外紫外写入光栅的进展做了讨论。 相似文献
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Copy-paste forgery is a very common type of forgery in JPEG images.The tampered patch has always suffered from JPEG compression twice with inconsistent block segmentation.This phenomenon in JPEG image forgeries is called the shifted double JPEG(SDJPEG) compression.Detection of SDJPEG compressed image patches can make crucial contribution to detect and locate the tampered region.However,the existing SDJPEG compression tampering detection methods cannot achieve satisfactory results especially when the tampered region is small.In this paper,an effective SDJPEG compression tampering detection method utilizing both intra-block and inter-block correlations is proposed.Statistical artifacts are left by the SDJPEG compression among the magnitudes of JPEG quantized discrete cosine transform(DCT) coefficients.Firstly,difference 2D arrays,which describe the differences between the magnitudes of neighboring JPEG quantized DCT coefficients on the intrablock and inter-block,are used to enhance the SDJPEG compression artifacts.Then,the thresholding technique is used to deal with these difference 2D arrays for reducing computational cost.After that,co-occurrence matrix is used to model these difference 2D arrays so as to take advantage of second-order statistics.All elements of these co-occurrence matrices are served as features for SDJPEG compression tampering detection.Finally,support vector machine(SVM) classifier is employed to distinguish the SDJPEG compressed image patches from the single JPEG compressed image patches using the developed feature set.Experimental results demonstrate the efficiency of the proposed method. 相似文献
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粤绣是中国四大名绣之一,而潮绣又是粤绣组成的重要分支。在潮绣发展过程中,结合外来花边工艺形成的抽纱工艺,既是潮绣的拓展又是潮绣家族中一只美丽的奇葩。而当下,此两种民间工艺只能作为非物质文化遗产来申报,其传承堪忧。 相似文献
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主要针对既有设备中的64D半自动闭塞制式,与最新的计算机联锁设备的过渡结合展开论述,为计算机联锁设备与64D半自动闭塞制式的结合提供了一种较为理想的方法。 相似文献
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GSM-R场强覆盖测试采样间距探讨 总被引:1,自引:1,他引:0
从电波传播的统计特点出发,针对目前我国GSM-R移动通信场强测试的采样间距进行了分析,在既有GSM-R线路上对国外应用的不同采样间距进行了对比测试,认为GSM-R移动通信系统的场强测试采样间距在小于Lee氏定律的情况下都是可以满足要求的。 相似文献
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本文就到达场与驼峰联系电路在实际应用当中存在的一些不足之处进行了改动,解决了长期困扰在运营工作当中的实际问题,尤其是雷害频繁的地区曾多次发生类似问题。本文就事故的产生、危害及解决的办法进行了论述。 相似文献