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With the rapidly rising interest in geographic information system (GIS) contents, a large volume of valuable map data has been unlawfully distributed by pirates. Therefore, the secure storage and transmission of classified national digital map datasets have been increasingly threatened. As the importance of secure, large-volume map datasets has increased, vector map security techniques that focus on secure network and data encryption have been studied. These techniques are required to ensure access control and prevent illegal copying of digital maps. This paper presents perceptual encryption on the vector compression domain for copy protection and access control of vector maps. Our algorithm compresses all vector data of polylines and polygons by lossless minimum coding object (MCO) units and perceptually encrypts using two processes using the mean points and directions of MCOs. The first process changes the position of vector data by randomly permuting the mean points of MCOs, the so-called position encryption. The second process changes the geographic shape by circularly encrypting the directions of vertices in MCOs by the XOR operator. Experimental results have verified that our algorithm can encrypt GIS digital maps effectively and simply and can also improve the compression ratio, unlike general data encryption techniques, and thus, our algorithm is very effective for a large volume of GIS datasets. 相似文献
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QuEChERS-超高效液相色谱-串联质谱法测定柑橘中呋虫胺和螺虫乙酯残留量 总被引：1，自引：0，他引：1
目的 建立QuEChERS-超高效液相色谱-串联质谱法(ultra performance liquid chromatography-tandemmass spectrometry,UPLC-MS/MS)同时测定柑橘中呋虫胺及螺虫乙酯残留量的分析方法.方法 样品采用QuEChERS方法,经1％甲酸乙腈涡旋振荡提取,无... 相似文献
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目的 建立超高效液相色谱-串联质谱法(ultra performance liquid chromatography-tandem mass spectrometry, UPLC-MS/MS)测定干辣椒中氰氟虫腙和氯虫苯甲酰胺残留量的分析方法。方法 干辣椒样品经乙腈匀浆提取, 氨基固相萃取小柱净化, 甲醇/水(50:50, V:V)定容, 以反相C18色谱柱(100 mm×2.1 mm, 1.7 μm)分离, 0.1%甲酸-水和甲醇作为流动相进行梯度洗脱, 多反应监测模式下进行超高效液相色谱-串联质谱测定、基质匹配标准溶液外标法定量。结果 2种新型杀虫剂在5~500 μg /L范围内线性关系良好, 相关系数均大于0.999, 定量限为0.008~0.01 mg /kg; 在高、中、低3个加标水平下的回收率为80.4%~94.9%, 相对标准偏差在0.9%~8.7%之间。结论 方法简单、快速、灵敏高、准确可靠, 可操作性强, 适合测定干辣椒中氰氟虫腙和氯虫苯甲酰胺残留量。 相似文献
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