Submarine landslide identified in DLW3102 core of the northern continental slope,South China Sea

In this paper, we take DLW3101 core obtained at the top of the canyon(no landslide area) and DLW3102 core obtained at the bottom of the canyon(landslide area) on the northern continental slope of the South China Sea as research objects. The chronostratigraphic framework of the DLW3101 core and elemental strata of the DLW3101 core and the DLW3102 core since MIS5 are established by analyzing oxygen isotope, calcium carbonate content, and X-Ray Fluorescence(XRF) scanning elements. On the basis of the information obtained by analyzing the sedimentary structure and chemical elements in the landslide deposition, we found that the DLW3102 core shows four layers of submarine landslides, and each landslide layer is characterized by high Si, K, Ti, and Fe contents, thereby indicating terrigenous clastic sources. L1(2.15–2.44 m) occurred in MIS2, which is a slump sedimentary layer with a small sliding distance and scale. L2(15.48–16.00 m) occurred in MIS5 and is a debris flow-deposited layer with a scale and sliding distance that are greater than those of L1. L3(19.00–20.90 m) occurred in MIS5; its upper part(19.00–20.00 m) is a debris flow-deposited layer, and its lower part(20.00–20.90 m) is a sliding deposition layer. The landslide scale of L3 is large. L4(22.93–24.27 m) occurred in MIS5; its upper part(22.93–23.50 m) is a turbid sedimentary layer, and its lower part(23.50–24.27m) is a slump sedimentary layer. The landslide scale of L4 is large.     

Hydroacoustic estimates of fish biomass and spatial distributions in shallow lakes

We conducted acoustical surveys with a horizontal beam transducer to detect fish and with a vertical beam transducer to detect depth and macrophytes in two typical shallow lakes along the middle and lower reaches of the Changjiang(Yangtze) River in November 2013. Both lakes are subject to active fish management with annual stocking and removal of large fish. The purpose of the study was to compare hydroacoustic horizontal beam estimates with fish landings. The preliminary results show that the fish distribution patterns dif fered in the two lakes and were af fected by water depth and macrophyte coverage. The hydroacoustically estimated fish biomass matched the commercial catch very well in Niushan Lake, but it was two times higher in Kuilei Lake. However, acoustic estimates included all fish, whereas the catch included only fish 45 cm(smaller ones were released). We were unable to determine the proper regression between acoustic target strength and fish length for the dominant fish species in the two lakes.     

Regional Characteristics and Causes of Haze Events in Northeast China

Northeast China experiences severe atmospheric pollution, with an increasing occurrence of heavy haze episodes. However, the underlying forces driving haze formation during different seasons are poorly understood. In this study, we explored the spatio-temporal characteristics and causes of haze events in Northeast China by combining a range of data sources(i.e., ground monitoring, satellite-based products, and meteorological products). It was found that the ‘Shenyang-Changchun-Harbin(SCH)'city belt was the most polluted area in the region on an annual scale. The spatial distribution of air quality index(AQI) values had a clear seasonality, with the worst pollution occurring in winter, an approximately oval-shaped polluted area around western Jilin Province in spring, and the best air quality occurring in summer and most of the autumn. The three periods that typically experienced intense haze events were Period I from mid-October to mid-November(i.e., late autumn and early winter), Period II from late-December to February(i.e., the coldest time in winter), and Period III from April to mid-May(i.e., spring). During Period I, strong PM_(2.5) emissions from seasonal crop residue burning and coal burning for winter heating were the dominant reasons for the occurrence of extreme haze events(AQI 300). Period II had frequent heavy haze events(200 AQI 300) in the coldest months of January and February, which were due to high PM_(2.5) emissions from coal burning and vehicle fuel consumption, a lower atmospheric boundary layer, and stagnant atmospheric conditions. Haze events in Period III, with high PM_(10) concentrations, were primarily caused by the regional transportation of windblown dust from degraded grassland in central Inner Mongolia and bare soil in western Jilin Province. Local agricultural tilling could also release PM_(10) and enhance the levels of windblown dust from tilled soil. Better control of coal burning, fuel consumption, and crop residue burning in winter and autumn is urgently needed to address the haze problem in Northeast China.     

Responses of soil moisture to vegetation restoration type and slope length on the loess hillslope

Soil moisture, a critical variable in the hydrologic cycle, is highly influenced by vegetation restoration type. However, the relationship between spatial variation of soil moisture, vegetation restoration type and slope length is controversial. Therefore, soil moisture across soil layers (0-400 cm depth) was measured before and after the rainy season in severe drought (2015) and normal hydrological year (2016) in three vegetation restoration areas (artificial forestland, natural forestland and grassland), on the hillslopes of the Caijiachuan Catchment in the Loess area, China. The results showed that artificial forestland had the lowest soil moisture and most severe water deficit in 100-200 cm soil layers. Water depletion was higher in artificial and natural forestlands than in natural grassland. Moreover, soil moisture in the shallow soil layers (0-100 cm) under the three vegetation restoration types did not significantly vary with slope length, but a significant increase with slope length was observed in deep soil layers (below 100 cm). In 2015, a severe drought hydrological year, higher water depletion was observed at lower slope positions under three vegetation restoration types due to higher transpiration and evapotranspiration and unlikely recharge from upslope runoff. However, in 2016, a normal hydrological year, there was lower water depletion, even infiltration recharge at lower slope positions, indicating receiving a large amount of water from upslope. Vegetation restoration type, precipitation, slope length and soil depth during a rainy season, in descending order of influence, had significant effects on soil moisture. Generally, natural grassland is more beneficial for vegetation restoration than natural and artificial forestlands, and the results can provide useful information for understanding hydrological processes and improving vegetation restoration practices on the Loess Plateau     

Spatial differentiation in stable isotope compositions of surface waters and its environmental significance in the Issyk-Kul Lake region of Central Asia

Stable isotope values of oxygen(~(18)O) and hydrogen(~(2)H) of surface waters were used to study the origin and environmental significances in the Issyk-Kul basin of Kyrgyzstan in Central Asia, which is the most important intermountain basin in the modern Tien Shan orogen. This study is the first analysis of hydrochemical spatial differentiation in the stable isotopes of surface waters in this watershed.75 samples were collected from rivers, springs, lakes,rain and snow during the rainy season in July and August of 2016. Stable isotopes of ~(18)O and ~(2)H were studied for all samples, and cation ratios(Sr/Ca and Mg/Ca) were also determined for lake water samples.Stable isotope values from precipitation scattered around the Local Meteoric Water Line(determined from Urumqi Station of the global network of isotopes in precipitation(GNIP)), together with values of the Deuterium excess parameter(d) from 15.3‰ to30.5‰, with an average of 19.8‰, indicating that the moisture sources are primarily from regions with low relative humidity. The δ~(18)O and δ~(2)H values were significantly different between the river and lake samples, indicating that regional evaporation caused the isotopic enrichment of lake water. Geospatial autocorrelation, measured by Moran's I coefficient,indicated weak spatial autocorrelation within stable isotopes of oxygen and hydrogen in the surface waters of the studied area, which is primarily an effect of climate during the water chemistry evolution. The cation ratios Sr/Ca and Mg/Ca in lake water samples were not correlated with the concentration of total dissolved solids, but did show correlation with stable isotopic values, which is significant for paleoenvironmental reconstruction.     

相变存储材料Ge1Sb2Te4和Ge2Sb2Te5薄膜的结构和电学特性研究

采用射频磁控溅射方法制备了两种用于相变存储器的Ge₁Sb₂Te₄和Ge₂Sb₂Te₅相变薄膜材料,对其结构、电学输运性质和恒温下电阻随时间的变化关系进行了比较和分析.X射线衍射(XRD)和原子力显微镜(AFM)的结果表明:随着退火温度的升高,Ge₁Sb₂Te₄薄膜逐步晶化,由非晶态转变为多晶态,表面出现均匀的、     

非稳腔主动式直接获取纳秒近似无衍射贝塞尔绿光

通过对基于轴棱锥的贝塞尔谐振腔和贝塞尔-高斯谐振腔的研究,设计了一台腔内倍频Nd:YAG纳秒近似无衍射贝塞尔绿光激光器. 非稳激光器谐振腔由轴棱锥和凸面镜组成. 实验采用单灯脉冲抽运激光增益介质Nd:YAG晶体,倍频晶体选用KTP. 当抽运电压为350 V时,由主动式直接产生纳秒近似零阶贝塞尔绿光,其脉冲宽度为55.1 ns,波长为532 nm,线宽为0.8 nm,近似无衍射零阶贝塞尔绿光的中心光斑直径为192 μm. 利用Fresnel-Kirchhoff 衍射积分和Fox-Li迭代法,通过数值计算得出     

阶变折射率轴棱锥产生局域空心光束

提出利用折射率成阶跃性变化的轴棱锥产生局域空心光束(bottle beam).讨论了折射率沿径向成阶跃式减小或增加两种模型,从几何光学角度分析了它们产生bottle beam的原理,利用衍射积分理论数值模拟两种轴棱锥光传输的光场分布和不同距离处的二维光斑图,研究结果表明折射率沿径向阶跃减小的轴棱锥产生单个bottle beam,而折射率沿径向阶跃增加的轴棱锥产生具有周期再现的bottle beams.bottle beam在原子引导和囚禁、光学俘获及光镊等方面有广泛的应用, 因此本文的研究对bottle     

(2+1)维 Korteweg-de Vries 方程的传播孤子及混沌行为

利用一个投射方程和变量分离法,得到了(2+1)维 Korteweg-de Vries (KdV) 方程的新显式精确解.根据得到的孤立波解,构造出 KdV 方程的传播孤子结构. 利用一个新的混沌系统研究了孤子的混沌行为.     

增强型AlGaN/GaN高电子迁移率晶体管高温退火研究

深入研究了两种增强型AlGaN/GaN高电子迁移率晶体管(HEMT)高温退火前后的直流特性变化.槽栅增强型AlGaN/GaN HEMT在500 ℃ N₂中退火5 min后,阈值电压由0.12 V正向移动到0.57 V,器件Schottky反向栅漏电流减小一个数量级.F注入增强型AlGaN/GaN HEMT在 400 ℃ N₂中退火2 min后,器件阈值电压由0.23 V负向移动到-0.69 V,栅泄漏电流明显增大.槽栅增强型器件退火过程中Schottky有效势垒