Landscape Dynamics and Driving Factors in Da＇an County of Jilin Province in Northeast China During 1956-2000

The landscape pattern of Da＇an County, Northeast China has undergone significant changes since the 1950s as a result of climatic change and human activities. The aim of this paper is to quantitatively study landscape pattern and its spatial dynamics of Da＇an County at the landscape level over the nearly 50-year span. Patch dynamics were examined according to land use and land cover change processes built from a series of images, as well as topographic maps, and temporal patterns built from landscape pattern metrics. The transition matrix of landscape patch types and changes of various landscape metrics were applied. The results showed that, from 1956 to 2000, the landscape within the study area had undertaken a complicated evolution in landscape structure and composition. The outstanding characteristic is that saline-alkali land increased and grassland decreased. As some smaller patches amalgamated, the heterogeneity of patch decreased. All those changes were the synthetic result of both climatic and anthropogenic influences, but the predominant factor was different in different parts. In the southern part of the study area, the landscape pattern changes resulted from the modification of climate obviously, while in the northern part, the landscape pattern changes were mainly caused by human activities, such as the conversion between farmland and saline-alkali land. This phenomenon showed that human activities played more important role in the north than in the south of Da＇an County.     

附有标高刻度的三维立体剖面图的模型方法及其在垂直形变分析中的应用

提出了一种用于垂直形变分析的附有标高刻度的三维立体剖面图的全新模型方法 ,介绍了用这一模型方法建立国家复测水准网三维立体剖面图模型的过程。使用表明 ,这一模型方法与目前常用的三维空间表示方法相比 ,在定量、定位分析水准点的沉降变化时具有直观、快速等优点。     

新疆拜城黑孜尔水库垂直形变观测与现今断层活动特征

根据跨断层定点水准、基线观测资料和垂直形变的水准高程观测数据分析,黑孜尔断裂 Ｆ２定点水准的垂直位移量为 ０． １４ ｍｍ／ａ,基线缩短量为 ０． ４８ ｍｍ／ａ,断层滑动角■≈３７°,现今垂直形变速率为 ０． ６９３ ｍｍ／ａ。结合地震活动和区域地质构造研究,认为黑孜尔断裂近期水平活动强度大于垂直运动强度,该区在未来１～３年内仍可能发生６级以上地震。     

基于DEM的山地地理可照时数空间分布估算统计模型——以重庆为例

为了建立合理、准确且便于估算和应用的山地地理可照时数空间分布模型,本文以重庆为例,首先利用分布式模型估算了30 a平均年和各月可照时数,并利用基于气象行业标准得到的理论值进行了验证;其次,以栅格单元为统计样本,建立了基于地形尺度的可照时数估算的统计模型。结果表明:(1)基于分布式模型的模拟结果具有较高可信度,除10月外,其他各月和年的相对误差均小于10%,且东北和东南部的相对误差较中西部高。(2)西部方山丘陵区的可照时数高,中部平行岭谷区次之,东北和东南部低。冬季可照时数的空间异质性最大,夏季次之,春秋季接近,均较小。(3)各月和年可照时数与主要地理和地形因子之间的相关关系均表现为极显著性,各月复相关系数在0.7929~0.8277,年复相关系数为0.8522。(4)重庆可照时数估算统计模型在一定程度上简化了分布式模型的计算步骤和计算量,便于其应用,并可为其他地区估算可照时数提供方法参考。     

相对剥夺视角下的乡村旅游地居民不规范行为研究 ——以江西婺源县李坑、思溪为例

居民不规范行为危害性极大,传统相关研究多基于社会交换视角,存在一定局限。相对剥夺理论在研究人们的不规范行为上存在一定优势,但鲜有应用于旅游研究。以社区问题明显的李坑、思溪两村落为例,结合相对剥夺理论对居民不规范行为的成因和形式等进行了定性分析。与传统研究不同,发现居民不规范行为与其对旅游负面影响的纵向感知并无直接关系,而主要与横向剥夺感相关。研究表明,相对剥夺理论或可作为居民旅游态度和行为研究的新视角,并在预防和管控旅游地社区问题方面具有重要现实意义。     

围海造陆条件下排海高温浓盐水对渤海湾温盐场分布影响模拟及预测

自2000年以来围绕渤海湾的围海工程剧增,致使工程区附近潮流场发生变化,进而影响排海高温浓盐水的时空分布特征。本文通过建立2000年和2015年两种不同岸线、地形条件下的三维数学模型对渤海湾沿岸3个电厂高温浓盐水表层排海问题进行模拟,研究结果表明,渤海湾的潮流场和高温浓盐水输移扩散特征在近十几年发生了较大变化:工程后,渤海湾平均盐度增大0.203,平均温度升高了0.105℃,同时曹妃甸附近海域浓盐水输移扩散速度明显增加。增大排放口流量至12.7 m3/s,湾内最高温度为26.46℃,较2015年最高温度增加了2.72℃。本文模型可准确模拟及预测排海废水盐度、温度分布特征,为合理布置水电联产设备排放口的位置提供理论基础。     

X-ray activity from different types of stars

X-ray emission is an important indicator of stellar activity. In this paper, we study stellar Xray activity using the XMM-Newton and LAMOST data for different types of stars. We provide a sample including 1259 X-ray-emitting stars, of which 1090 have accurate stellar parameter estimations. Our sample size is much larger than those used in previous works. We find a bimodal distribution of the X-ray to optical flux ratio(log(fX/fV)) for G and K stars. We interpret that this bimodality is due to two subpopulations with different coronal heating rates. Furthermore, using the full widths at half maxima calculated from Hα and Hβ lines, we show that these stars in the inactive peaks have smaller rotational velocities. This is consistent with the magnetic dynamo theory that presumes stars with low rotational velocities have low levels of stellar activity. We also examine the correlation between log(fX/fV) and luminosity of the excess emission in the Hα line, and find a tight relation between the coronal and chromospheric activity indicators.     

改进分数阶达尔文粒子群的多Renyi熵图像分割算法

针对智能优化图像分割算法易陷入局部最优、分割精度不高等问题,本文融合改进的分数阶达尔文粒子群算法和二维Renyi熵多阈值,提出了一种新的多阈值遥感图像分割算法。算法利用粒子自身进化信息来定义进化因子,结合进化因子并利用高斯图函数调整分数阶次a系数以实现精确计算和快速收敛;根据局部最优概率因子对局部最优位置进行Levy飞行随机扰动以提高算法跳出局部最优的能力;同时将二维Renyi熵单阈值扩展到多阈值分割上,并结合改进的分数阶达尔文粒子群算法,将二维Renyi熵多阈值应用于遥感图像分割中仿真结果表明,与其他2种智能优化分割算法相比,本文分割算法在细节处理和分割精度上均有明显优势,在PRI上至少提升7.27%、VOI至少降低6.5%、GCE至少降低10.4%.     

寒武纪生物大爆发之后的底栖生态系统工程建造者:以河南地区为例

扰动生物作为生态系统工程建造者,通过对沉积底质的改造直接影响沉积物和水体之间的相互作用(营养物质的循环、迁移和存储),对底栖生态系统工程有重要的影响.遗迹化石作为底栖生物活动的载体,为研究寒武纪大爆发之后底栖生态系统工程建造者的演化规律,并评价底栖生态系统工程建造者对生态系统工程产生的影响提供了依据.对河南地区8个寒武...