Magnetic characteristics and its environmental implications of core YSJD-86GC sediments from the southern South China Sea

Sediments of core YSJD-86GC （referred to as 86GC） collected from the southern South China Sea were selected for environmental magnetic studies. Combined with the published chronological framework, sediment magnetic properties were revealed for the study area since the MIS3 stage. The rock magnetic results indicate that low-coercivity magnetite is the main magnetic mineral within the sediments. Also, a certain amounts of hematite are present. The King plot and Day plot, which reflect the magnetic particle size, show that fine-grained pseudo-sin- gle-domain phase magnetic particles dominate the magnetic minerals in the sediments. Comparison of magnetic parameters and geochemical indicators show that magnetic properties of core 86GC sediments reflect a terrigenous input. Simultaneously, magnetic characteristics of the stud- ied sediment are influenced by the quantity of terrigenous sediment input, oxidation-reduction conditions of the provenance area, and the transportation environment and distance. Sea level fluctuation caused by global climate change was the main factor for variation in concentration of magnetic minerals and magnetic particle size of thestudied core sediments. Thus, variation of sediment magnetic properties in the study area can be used as an indirect indicator of sea level fluctuation.     

Thermal diffusivity determination of solids by time-domain photoacoustic piezoelectric technique

Thermal–physical property is one of the most important properties of materials. The conventional frequency-domain photoacoustic piezoelectric(PAPE) technique has been developed as an important method for thermal diffusivity determination. In this paper, the PAPE technique is extended to time domain(TD). First, based on a simplified thermoelastic model, the TD PAPE theory under square-wave-modulated excitation was developed,the dependence of the TD PAPE signal on modulation frequency as well as material parameters was obtained, and the determination of thermal diffusivity was simulated and theoretically analyzed. Second, the experimental system and the corresponding measurement method were established. Third, thermal diffusivities of various standard samples, such as copper, aluminum, and nickel, were measured, and the effectiveness of the technique was verified. The results show that the TD PAPE technique can provide a simple, fast and effective way for thermal diffusion study.     

Detecting the micro-defects in the GaAs materials by time resolved emissions

The GaAs material is a major semiconductor material, and it has high electron transfer rate and direct transition energy band structure. The devices and inte-grated circuits fabricated on the GaAs substrates have a lot of advantages such as high speed information processing. Small perturbations in the manufacturing of GaAs materi-als can lead to defects. The defects in the GaAs materials can degrade the performance of materials. A new method is presented in this paper for detecting the micro-defects in GaAs materials by using time resolved emissions. In this method, the micro-defects in GaAs materials are detected by making use of the photon emission features of micro- defects. The strength of the emitted photons from the micro-defects is increased by applying the electric current or the periodic pulse signals to GaAs materials. The single-photon detector is used to detect the photon emissions of the micro-defects. The time resolved photon emissions and single-photon detection are used to record and compare the amounts of the emitted photons that come from the given regions of the normal GaAs materials and the defective GaAs materials. A lot of experimental results show that the micro-defects in the GaAs materials can be detected by using the method proposed in this paper.     

《春秋左氏传》(卷1)通假现象分析

<正>0引言《春秋左氏传》又称《左氏春秋》或简称《左传》,它是中国历史上彪炳千秋的重要历史文献。"春秋"本为东周时期纪事史书的通称,但由于仅有鲁国的"春秋"得以流传,故《春秋》也就成了鲁国"春秋"的代名词。而《左传》又是为《春秋》的三家之中公认最好的一家。《春秋》原书文字简练,犹如记事年表,《左传》大量补充了《春秋》的史实,并用文学的语言出色描写了当时的历史事件,历来被奉为经典。中国古人一直有尚古传统,《左传》的文辞也就自然被后来的读书人甚至是史家奉为     

Formation of highly crystalline maghemite nanoparticles from ferrihydrite in the liquid phase

Fe5O7（OH）·4H2O ferrihydrite is a low-crystal- linity antiferromagnetic material, γ-Fe2O3 （maghemite） magnetic nanoparticles were prepared from a ferrihydrite precursor, by chemically induced transformation in FeCl2/ NaOH solution. The magnetization, morphology, crystal structure and chemical composition of the products were determined by vibrating sample magnetometry, transmission electron microscopy, X-ray diffraction （XRD）, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy （XPS）. Ferrihydrite underwent aggregation growth and transformed into α-FeO（OH） （goethite） particles, which subsequently transformed into γ-Fe2O3 nanoparticles, that became coated with NaCI. The γ-Fe2O3 particles had a flake-like morphology, when prepared from 0.01 mol/L FeCl2 and a FeCl2：NaOH molar ratio of 0.4. The γ-Fe2O3 particles were more spherical, when prepared from a FeCl2：NaOH molar ratio of 0.6. The Fe content of the flake-like particles was lower than that of the spherical particles. Their magnetizations were similar, and the coercivity of the flake-like particles was larger. The differences in morphology and magnetization were attributed to the surface effect, and the difference in coercivity to the shape effect.     

黏弹阻尼对一维杆状声子晶体能带结构频移的影响

为了明确黏弹阻尼对声子晶体能带结构的影响,根据黏弹材料的标准线性固体模型,利用平面波展开法的迭代算法对一维黏弹材料声子晶体的能带结构进行了理论计算和对比分析。与弹性模量为常数的完全弹性材料相比,黏弹材料由于其复模量的频率相关性,储能模量和损耗模量对声子晶体的能带结构都有重要影响,特别是损耗模量对声子晶体能带结构的影响在阻尼峰值附近的频率范围不容忽视。位于此频率范围的能带被调向更高频而其他范围的能带基本不变,从而使能带下方带隙增宽而上方带隙变窄。损耗模量对能带结构的这一特定调节作用为黏弹性阻尼材料应用于声子晶体提供了一定的理论基础,也为获得宽频带隙提供了一种新的方法。     

气体流速对FCVA技术制备nc-ZrC/a-C：H复合膜的影响?

采用磁过滤阴极真空弧(FCVA)技术,室温下通入C2H2在Si(100)与304不锈钢片上制备nc-ZrC/a-C:H复合薄膜.采用XRD、Raman、XPS、SEM-EDS研究了薄膜的成分及微观结构,利用纳米力学探针和摩擦磨损仪测试薄膜的硬度及摩擦磨损性能.主要讨论了不同C2H2气体流速对复合膜成分、结构及其性能的影响,研究结果表明:C2H2气体流速由20mL·min-1增加到70mL·min-1时,薄膜中的C原子分数逐渐升高;气体流速超过70mL·min-1后,C原子分数趋于平稳(约为75%).随着气体流速的增加,薄膜硬度呈现先增后减的趋势,当气体流速为40mL·min-1时(C原子分数约为65%),制备的薄膜综合机械性能达到最佳(硬度41.49GP,摩擦因数0.25).     

MEVVA离子束技术的发展及应用

金属蒸汽真空弧放电能够产生高密度的金属等离子体.通过二或三电极引出系统,可以把金属等离子体中的金属离子引出,并加速成为载能的金属离子束,这是MEVVA离子源技术.将载能离子束用于离子注入,可以实现材料表面改性.经过MEVVA源离子注入处理的工具和零部件,改性效果显著,因此MEVVA离子源在离子注入材料表面改性技术中得到很好的应用.另一方面,利用弯曲磁场把等离子体导向到视线外的真空靶室中的同时,过滤掉真空弧产生的液滴(大颗粒),当工件加上适当的负偏压时,等离子体中的离子在工件表面沉积,可以得到高质量的、平整致密的薄膜,称为磁过滤等离子体沉积.是一种先进的薄膜制备的新技术.此外,将MEVVA离子注入与磁过滤等离子体沉积相结合的复合技术,可以首先用离子注入的方法改变基材表面的性能,再用磁过滤等离子体沉积的方法制备薄膜,可以极大的增强薄膜与基材的结合强度,得到性能极佳的薄膜.适用于基材与薄膜性能差别大,结合不易的情况(例如陶瓷、玻璃表面制备金属膜).本文简要介绍了MEVVA离子注入技术、磁过滤等离子体沉积技术和MEVVA复合技术的发展和应用状况.     

壳聚糖与DNA相互作用的单分子方法研究

利用原子力显微镜与磁镊技术研究不同浓度的壳聚糖与多种DNA分子的作用,对其凝聚形态及力谱曲线进行观察。在恒力情况下,壳聚糖与DNA的电荷比k分别为3和4时,从DNA的力谱曲线上可以看见0.2~0.5μm左右的跳跃阶梯及线性增长区域,原因可能是壳聚糖-DNA聚合物中出现了环状、棒状及球状结构;利用原子力显微镜观察壳聚糖与λ-DNA及bpr322-DNA作用后的凝聚形态,发现随着壳聚糖与DNA电荷比k的增加,球状与棒状聚合物的比例明显减小,而且凝聚物的尺寸也整体减小。最后根据实验结果,建立了壳聚糖导致DNA构象变化的直观模型。     

浅析发电机反时限过激磁保护误动作分析策略

做好继电保护动作分析,及时制定改进措施是防止继电保护误动、拒动的关键。通过发电厂的一个典型实例,对发电机反时限过激磁保护不正确动作的处理分析过程进行了详细说明,并从专业管理和技术方面,提出发电厂继电保护不正确动作处理措施和应注意的事项,阐述了分析继电保护不正确动作的主要步骤和方法,以避免此类问题的重复发生。