Monitoring dynamic changes of global land cover types:fluctuations of major lakes in China every 8 days during 2000–2010

Remote sensing images can be used to delineate variations in the area of lakes and to assess the influence of environmental changes and human activities.However,because lakes are dynamic,results obtained from individual images acquired on a single date are not representative and do not accurately reflect ongoing changes.In this study,we used 8-day moderate resolution imaging spectroradiometer(MODIS)composite data from 2000 to2010 to map water surface changes over 629 lakes in China.We combined automatic extraction of training data and support vector machine classification to derive the spatial distribution of these large water bodies.The producer’s and user’s accuracies for MODIS images were91.06%and 89.81%,respectively,when compared with interpretation results from 30 m resolution Landsat images taken on similar days.Area changes,variability,inundation intensity,and rainy seasons of the 629 lakes were analyzed based on this multi-temporal lake database.The total area of the 629 lakes increased over the study period,primarily as a result of the expansion of lake areas on the Tibetan Plateau.There were 12 lakes with a maximum area[1,000 km2,and six of these decreased in area from 2000to 2010.The shrinkages of Poyang Lake and Dongting Lake were-54.76 and-25.08 km2/a,respectively.The area of lakes on Tibetan Plateau,in northern Xinjiang,northeastern Inner Mongolia,and northeastern China varied little,while lakes on the Yangtze Plain,in southern Inner Mongolia,and central Xinjiang fluctuated considerably.Inundation intensity increased for lakes on the Tibetan Plateau,in northern Xinjiang,Heilongjiang,and Jilin,while inundation extent decreased in central Xinjiang,southern Tibet,southern Inner Mongolia,Sichuan,and on the Yangtze Plain.This study is an attempt to develop high-frequency specific land cover maps to improve applicability of general land cover maps.The lake products serve as an important supplement to hydrologic data.The lake database enables the generation of new land surface process models,which could improve the precision of simulations,based on more accurate observations of dynamic lake systems.     

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.     

基于偏最小二乘回归的鱼雷管峰压估计

采用偏最小二乘回归方法,经交叉有效性检验建立了鱼雷管峰压的回归方程.通过实验数据比较,该模型拟合精度较强,说明偏最小二乘回归是估算舰艇鱼雷发射内弹道特征参数的一种有效方法.     

WT-CFAR雷达杂波处理器

根据子波变换的多尺度分析理论,构造了一种恒虚警雷达染处理器。并对子波分解尺度的选取进行了分析,最后对杂波环境下的雷达信号进行处理,验证了该方法的有效性和鲁棒性。     

雕刻系统中的仿形测试与三维成型技术研究

介绍了作者对雕刻行业ＣＡＴ／ＣＡＤ／ＣＡＭ系统进行研究开发所发取得的部分成果,其中包括浮雕轮廓仿形ＣＡＴ装置的实现,测量数据的筛选与处理方法Ｄｍａｘ浮雕曲面造型算法及数控加工文件的形成等。     

单片机应用系统的自动恢复技术

从软件的角度简要讨论了单片机系统在遭受干扰后,及时发现和拦截失去控制的程序流向并尽可以无扰动地恢复系统正常工作状态的各种方法和措施。     

苯乙酮制备实验的探讨与改进

对高师有机化学实验教材中苯乙酮的制备实验进行了探讨与改进,使用升华无水 ＡｌＣｌ３作催化剂,在ＡｌＣｌ３／Ａｃ２Ｏ摩尔比为２．３～２．５时取得了较好的实验结果。制备收率由原来５６％提高到７０％。     

地下水资源超采的分类探讨

从地球系统科学及社会可持续发展的高度,论述了地下水超采对环境的影响,重点探讨了地下水与地下水资源的区别,地下水资源超采的科学含义,对现行地下水资源超采分类方法进行了评述并提出了新的分类方法,最后对如何保证地下不资源的可持续开发提出了一些建议和措施。     

过氧杂多化合物的合成与催化性能(Ⅰ)──Dawson结构的过氧钽杂多化合物的合成与表征

合成了过氧磷钨杂多酸盐α２Ｋ７－ｍＨｍ［Ｐ２Ｗ１７（ＴɑＯ２）Ｏ６１］·ｘＨ２Ｏ（Ｍ＝Ｋ,ＴＭＡ,ＴＥＡ,ＴＢＡ）,并且用极谱－循环伏安、ＩＲ、ＵＶ吸收光谱、ＸＰＳ、ＸＲＤ、３１ＰＮＭＲ、１８３ＷＮＭＲ谱进行表征     

曲面投影轮廓线在奇点处光滑时的曲线特征

对凹回转面可见轮廓线的投影在奇点附近仍光滑的情况下,分析了可见轮廓线本身与奇点对应点处的曲线特征以及可见轮廓线在其对称平面的投影图上配奇点对应的特征。对凹回转面可见轮廓线在奇点附近形状作了进一步的分析与研究。