基于模式噪声的数字视频篡改取证

为了实现视频信号的真实性鉴别,提出一种基于模式噪声的数字视频篡改检测算法.由于成像传感器的非理想性,每一种数码摄像机都会输出一种相对稳定的残留噪声,通过维纳小波滤波器从视频的每一帧中提取这一噪声,将一段视频中的每帧噪声取平均值,从而建立模式噪声.当一段视频遭受篡改处理时,通过比较待鉴别帧的噪声与模式噪声之间的相关性,利用实验经验阈值判断,定位篡改区域.实验结果证明该方法能够对视频篡改进行有效的检测.     

调合石蜡的相平衡参数和相变动力学特性

使用正规溶液模型的Scatchard-Hildebrand方程对调合石蜡的熔点、浊点以及固-液和组元相变速率进行了计算.以切片石蜡作为被调合石蜡的计算结果表明,烷烃的相变温度和切片石蜡相近时,该烷烃对调合石蜡的熔点、浊点以及相变动力学特性影响较小.增加C22类轻质烷烃的质量分数,调合石蜡的熔点、浊点降低;熔程内较低温度下,轻质烷烃相变速率变慢,重质烷烃相变速率变快.增加C35类重质烷烃的质量分数,调合石蜡的浊点升高,熔点呈现复杂的变化,对C24以下烷烃的相变速率几乎没有影响,C25以上烷烃在熔程内较低温度下相变速率变慢.计算结果可以为相变储能中选用具有适当相变温度及相变动力学特性的调合石蜡提供指导.     

长纤维高速过滤器的运行动力学研究

为对长纤维高速过滤器的模拟分析、运行控制及效果预测提供理论依据,在深入分析长纤维高速过滤器深层过滤机理及积泥形态的基础上,结合试验观察,借鉴半经验、半理论模型,建立了用以表征长纤维高速过滤器运行特性的水头损失方程及传质动力学模型.通过大量试验测定和对初始滤速为30 m/h时的模型计算与实测结果的比较表明,除沉淀出水过滤前期滤出水浊度计算值与实测值误差较大外,其余各范围计算值均吻合良好,证明了假设的合理性及模型的有效性.     

基于专家系统的变电站监控信号智能处理系统

为了减轻变电站运行人员的工作负担,辅助故障快速判断,提高运行人员技术水平,在深入总结变电站异常和故障类型的基础上,构建了一个多层次的故障推理模型,结合网络拓扑技术,实现了一个基于专家系统的变电站监控信号智能处理系统.系统的监控信号分析处理功能全面,快速定位机制确保值班员能迅速确定故障信息所在间隔,能准确报告变电站主要故障,并结合专家知识库出具故障报告,提供故障处理指导.系统具备故障模拟及培训功能.该系统在变电站实际应用中取得了良好的效果.     

Pollen record and environmental evolution of Caotanhu wetland in Xinjiang since 4550 cal. a BP

This paper presents a multi-proxy reconstruction of the climate change in Caotanhu wetland using pollen, phytolith and charcoal records, and the data of loss of ignition （LOI）, grain size analysis, and susceptibility. Results reveal that between 4550 and 2500 cal. a BP, a dry climatic condition was not favorable for the accumulation of peat. Since 2500 cal. a BP, the climate became humid and the wetland developed with abundant freshwater aquatic plants, which contributed to peat accumulation. Never-theless, alternate periods of rain and dry climate occurred during that period. Between 2500 and 1810 cal. a BP （550 BC-140 AD）, the climate was more humid than at present. A lot of emerged plants, such as Phragmites, Typha and Sparganium, and freshwater green algae grew in the wetland which was sur-rounded by desert-steppe vegetation composed mainly of Chenopodiaceae, Artemisia, Compositae and Thalictrum. However, from 1810 to 1160 cal. a BP （140--790 AD）, the water level started to decrease and hydrophyte species reduced greatly, but some Phragmites still grew in the wetland and around it was desert vegetation with high proportion of Chenopodiaceae and Artemisia. Then from 1160 to 650 a BP （790--1300 AD）, it entered a period of desert-steppe with abundant mesic and xerophytic plants. And a lot of aquatic plants prevailed in the wetland. Here, what is noticeable is that percentages of arboreal pollen, consisting mainly of Betula and Picea, increased greatly and reached a maximal value of 27.2%, in which, Betula percentages rose to 23.2%. Hence, it is reasonable to conclude that Betula grew in the highland of the wetland, or Picea timberline shifted downward resulting in the increase of percentages of Betula and Picea pollen, which were transported into the wetland by flood or wind. But since 650 cal. a BP, desert vegetation prevailed around the wetland again with dominant Chenopodiaceae and Artemisia, and the climate was similar to modern one. Despite some aquatic plants still growing in the wetland at     

Detection of 2-thiaadamantanes in the oil from Well TZ-83 in Tarim Basin and its geological implication

Thermochemical sulfate reduction （TSR） causes increasing of sulfur content in the oils, reduction of oil quality, and produces a toxic and corrosive H2S which may take great adverse effect on health and equipment. Although there are several ways to identify presence of TSR in gas field, yet in the case of oil with low H2S content, it is still very difficult to identify TSR. 2-thiaadamantanes is one of the most effective indicators of TSR. This paper for the first time discovers 2-thiaadamantanes in the oil from Well TZ-83 in Tarim Basin. A silver nitrate silica gel chromatography was used to enrich the oil from low 2-thiaadamantanes content to the level that GC/MS and GC/MS/MS can detect. 2-thiaadamantanes were assigned by comparison of mass spectra with published data, and the fragmental ions in mass spectra were confirmed by MRM mode of GC/MS/MS. H2S gas produced in Tazhong area is thought to be generated from TSR since 2-thiaadamantanes were present in the oil.     

Signal and reference wave dually encrypted digital holographic system

We propose a secure digital holographic system with signal and reference waves dually encrypted. Two random phase masks are used to encrypt the images in the input and the Fourier planes. The reference beam is phase encoded by another random phase mask. The encrypted image and the key are recorded by a CCD camera. The data can be processed or transferred directly by computer. We theoretically and experimentally demonstrate encryption and decryption of multiple images and the results show a high quality and good fault tolerance.     

Phase transition in the subducted oceanic lithosphere and generation of the subduction zone magma

Two metamorphic processes, i.e. subsolidus dehydration and partial melting occurring in MORB, metasediments and peridotite of subducted oceanic lithosphere are discussed on the basis of available experimental work and phase equilibrium modeling. Phase diagrams of hydrous MORB show that in most cold subduction P-T （pressure-temperature） regimes a large portion of water in the basic layer has released below the onset of blueschist facies （〈 20 km）, and at a depth （60--70 km） of transition from lawsonite blueschist to lawsonite eclogite facies through glaucophane dehydration; only a smaller portion of water will escape from the slab through dehydration of lawsonite and chloritoid in the depth range suitable for arc magma formation; and a very small portion of water stored in lawsonite and phengite will fade into the deeper mantle. The role of amphibole for arc magma formation is still arguable. In cold subduction P-Tregimes, the dehydration of chlorite and talc in AI-poor metasediments, and chloritoid and carpholite in AI-rich metapelites at a depth around 80--100 km will make some con- tributions to the formation of arc magma. Comparatively, dehydration of serpentine in hydrated peri- dotite occurs at depths of 120--180 km, playing an important role in the arc magmatism. Subduction of oceanic crust along warm P-T regimes will cross the solidi at a depth over 80 km, resulting in partial melting under fluid-saturated and fluid-absent conditions in the metasediments involving biotite and phengite, and in the basic rocks involving epidote and amphibole. The melt compositions of the basic crust are adakitic at pressures 〈 3.0 GPa, but become peraluminous granitic at higher pressures.