排序方式： 共有107条查询结果，搜索用时 15 毫秒
41.
《Information processing & management》2023,60(4):103384
As the most ecologically active cryptocurrency platform, Ethereum has attracted the attention of many researchers. Leveraging its fully public transaction data, most existing analysis models all account interactions as a network and explores it from a static and global perspective. However, their work ignored the investigation of dynamic and microscopic features of accounts. Therefore, we conduct the first work about these features of different kinds of accounts on Ethereum. We select six account types on Ethereum, including exchanges, phishing, etc. Then we characterize and compare the dynamics of their transactions. Next, we construct a transaction ego network for each account, and investigate the network features from the perspective of microscopic structure. Experimental results show that different kinds of accounts have their own traits in terms of transaction features and properties of ego networks, which greatly contributes to understanding their roles. Additionally, there are obvious differences between normal accounts and illegal accounts in some characteristics such as transaction neighbors and interaction patterns. Moreover, we observe that criminal gangs may be participating in phishing scams. Finally, based on the conclusions of the account analysis, we design a variety of account features and use them for the account classification task. The experimental results prove that the dynamic and microscopic features we proposed are beneficial to distinguish different types of accounts. We believe our research can provide reference value for account classification tasks in Ethereum and other blockchains. 相似文献
42.
基于统计降尺度模型的博斯腾湖流域未来气温和降水变化趋势分析 总被引：3，自引：0，他引：3
SDSM统计降尺度模型是解决空间尺度不匹配问题的有效工具,它使气候变化响应研究得以在区域尺度上展开。本文将SDSM模型应用于博斯腾湖流域分析它的适用性,并对流域未来气温和降雨的变化趋势进行了预测。以日平均气温、最高气温、最低气温和日平均降雨量为预报量,选取合适的NCEP大气环流因子为预报因子,建立预报量与预报因子间的回归关系。利用1961年-1990年、1991年-2001年的实测数据和NCEP大气变量分别对SDSM模型进行率定和验证,效果较好。把HadCM3输出的A2、B2情景下的大气环流变量作为模型输入变量,模拟流域未来3个时期(2020s、2050s和2090s)的气温和降水变化。结果显示,流域未来日平均气温、最高气温和最低气温都呈现明显上升趋势,升高幅度为:日最高气温日平均气温日最低气温,且A2情景下气温增幅略大于B2情景;冬季气温增幅最小,夏季增幅最大;与全国降水的增加趋势不同,博斯腾湖流域未来的年降水量呈现明显减少趋势。分析结果可为博斯腾湖流域开展气候变化的水文响应研究以及气候变化的适应性研究提供科学依据。 相似文献
43.
青藏高原地面站春季积雪日数的时空演变特征 总被引：3，自引：1，他引：2
利用高原地区1962年-2004年64个地面站积雪资料,揭示了该地区春季积雪日数的时空演变特征,结果表明:①高原地区春季积雪日数空间分布局地差异显著,多雪区集中在巴颜喀拉山东段和藏北高原东南部,少雪区主要是藏南谷地、柴达木盆地以及川西干暖河谷地带;②空间分布可以概括为6种类型,青南高原东部型、藏北高原东部型、川西高原南部型、青藏高原东北部型、西藏东北部型以及川西高原东部型;③青南高原东部的春季积雪日数呈显著增长趋势,青藏高原东北部呈减少趋势,川西高原南部基本没有趋势变化,其余分区内各测站的线性变化趋势不完全一致,春季积雪日数仅在青南高原和川西高原东部地区存在由少变多的显著年代际变化,分别出现在1975年和1982年前后;④高原地区的春季积雪日数主要以准2年、准6年以及准10年的周期振荡为主。 相似文献
44.
Considering the demanding higher education context, university students are at risk to experience burnout symptoms such as emotional exhaustion, cynicism, and reduced professional efficacy. Theoretical models (e.g., Job Demands-Resources Model) state that burnout symptoms develop over time, vary between individuals, and bear adverse consequences. To date, the temporal development of student burnout symptoms within semesters, inter-individual differences in their development, and the role of their development for academic outcomes like student dropout are understudied. To complement this limited research, we used date of a three-wave longitudinal study with N = 1435 undergraduate students over one semester. First, we modeled unconditional second-order latent growth curves to examine the initial levels and trajectories of each burnout symptom (emotional exhaustion, cynicism, and reduced professional efficacy). We then modeled conditional second-order latent growth curves to examine whether initial levels and trajectories differed depending on students’ sociodemographic characteristics (gender, age, study progress, and academic major) and associated with students’ intentions to drop out from university. Results indicated a linear increase in student burnout symptoms over the semester. Sociodemographic differences existed in the initial levels of emotional exhaustion and reduced professional efficacy and the trajectories of each symptom. Generally, female, STEM, and higher- and lower- semester students were particularly affected by burnout symptoms. Further, higher initial levels and an increase in each symptom corresponded with higher dropout intentions. Summarizing, the results highlighted that student burnout symptoms increase as the semester progresses, seem more pronounced among certain student groups, and operate as strong predictors for dropout intentions. 相似文献
45.
汪恭勤 《温州职业技术学院学报》2012,12(4):66-68
人名是文化的镜像。古代女子名,有其构成特点,折射出文化内涵,而且被深深打上时代烙印。古代女子名的独特性及其在不同时代所呈现出的不同特点,反映了当时人们的命名习俗、婚姻制度及女性的社会地位等丰富的文化内涵。 相似文献
46.
模型检测是逻辑学和计算机科学中的一个重要研究领域,作为模态逻辑的一个重要分支时间逻辑,它的繁荣发展就出现在这一领域。模型检测是关于时间逻辑判定问题的研究,其研究的两类实体:一是关于刻画程序计算性质的逻辑公式,二是用来刻画程序的模型,模型检测的任务就是要校准这两种不同形式的信息——公式和模型——是否相一致。 相似文献
47.
北美聋人使用的美国手语作为人类语言之一有着与其他语言许多的共性,同时,作为一种独特的视觉空间语言,它也有着不同于有声语言的表达特点和语言特性。它不仅通过使用手势符号表词达意,还借助头部、面部表情和上身体态的变化辅助表达更为细腻的情感、语言和语法意义。美国手语中对时间信息的表达更是体现了其语言表达上的独特性。通过对美国手语时间信息表达方式较为系统的介绍和分析,探究其作为视觉空间语言所体现出的语言表达独特性。 相似文献
48.
The author's company, Informatics, an education and training provider, which already has its presence in 35 countries and territories spanning five continents, has a vision to be a global leader in providing lifelong learning services. In its pursuit for this vision, Informatics is keeping up with the rapid changes in the market and the threats and opportunities these changes bring. A pioneer in IT education and training in the region, Informatics is among the first to recognise the Internet as an important communication tool for learning. In recognising the need for individuals and corporations to embrace the lifelong learning philosophy to sustain competitiveness, Informatics ventured into e-learning—the essential facilitator for the lifelong learning process. Informatics established its e-learning portal in 1998, which was renamed Purpletrain.com. Purpletrain has been a success and Informatics will be speeding ahead with this vehicle to achieve its vision to be a global leader in lifelong learning. 相似文献
49.
黄河三角洲湿地资源时空变化分析 总被引：11，自引：1，他引：10
采用遥感与CIS相结合的方法,以1985年、1995年、2000年和2009牟为时间节点对黄河三角洲湿地资源的数量、变化速度、类型转换、重心位移等进行了提取和定量分析。研究结果表明,黄河三角洲湿地在研究期内的变化较为显著,各个时段的变化特点各有异同。整体上人工湿地呈逐年增长的趋势,1985年仅为零星分布,到了2009年则已处于主导地位,而且呈加速增长的趋势,2000年至2009年的增长速度达到了29．19km^2／a;近岸湿地、沼泽湿地等自然湿地整体上呈逐年退缩趋势,其中沼泽湿地的退缩最为显著,多转变为了人工湿地和农业用地;黄河三角洲湿地变化的主要驱动力为养殖等人工湿地的扩张,另外黄河口的改道对湿地格局的变化也有一定的影响,尤其对近岸湿地影响最为显著,而湿地重心的空间变化在1995年-2000年间也显著受到黄河口改道的影响;由于整体上湿地的转出数量大于转入数量,且以陆域湿地的转出为主,造成湿地重心呈向海一侧的“东向模式”变化。 相似文献
50.
山东省近海区域风能资源动力降尺度研究及储量估计 总被引：3，自引：2，他引：1
利用目前国内外广泛应用的中尺度数值模式系统MM5以及CALMET气象风场模块结合NCEP/NCAR再分析资料,选取近年来沿海年平均风速变化的平均年-2008年作为模拟年,结合模拟年地面和高空气象观测资料,对山东省近海风能资源进行动力降尺度模拟研究,得到不同高度1km×1km的风能资源分布状况。结合山东沿海岸及海岛自动气象站同期测风记录,对比分析了10m高度数值模拟结果与实际观测结果的相对误差。利用ARCGIS分析软件得到山东省近海范围内70m高度风能资源储量。结果表明:动力降尺度方法可用于较高分辨率的风能资源数值模拟,可作为区域风能资源评价分析的有效手段。 相似文献