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Search Results: 1 - 10 of 249496 matches for " 李 恺? "
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浅海水声信道动态响应建模与仿真研究
Dynamic Response Modeling and Simulation in Shallow Water Acoustic Channel
 [PDF]

赵晓群,, 立志
Modeling and Simulation (MOS) , 2013, DOI: 10.12677/MOS.2013.21001
Abstract:
水声通信系统必须与海洋通信信道相匹配才能达到良好的通信性能,如何对这样一个复杂多变的信道环境进行建模和仿真成为了一个研究的热点。本文主要研究浅海水声信道的仿真建模方法。利用BELLHOP高斯射线束跟踪法,对浅海信道的多途特性进行了建模;针对传统声线模型在信道动态响应建模上的不足,提出了一种新型的动态响应信道建模方法,仿真了信道的多途多普勒效应。分析了不同条件下信号的频谱规律。仿真结果与理论值相符,证明了模型的有效性。
Underwater acoustic communication system must match the communication channel in order to achieve a good performance. How to simulate for such a complex channel has become a hot research. This paper studied the shallow water acoustic channel modeling and simulation method. Using BELLHOP Gauss-ray beam tracing algorithm, modeled the multipath characteristics of the Shallow Water Acoustic Channel. Aiming at the lack of the traditional ray beam method, modeled a dynamic response channel. Simulated and analyzed the Doppler effect of the spectrum. The result showed that the Doppler shift was consistent with the theoretical value, which proved the effectiveness of the design.
考虑环境湍流作用的烟气上升路径方程

气象学报 , 1982, DOI: 10.11676/qxxb1982.008
Abstract: 本文利用我国的观测资料对中性层结时的烟气拾升路径作了细致的分析.发现抬升高度与距离之间符合幂次关系,但与不考虑环境湍流作用的"2"/3次律有系统偏离;这一偏离与烟流半径和高度的非线性关系相一致.上述事实与国外的一些观测结果均表明,环境湍流对烟气抬升的累积作用不容忽视.为此,提出了环境湍流与自生湍流的联合作用模式,由此导得的抬升路径方程可以满意地解释上述观测事实.模式还显示,卷挟速度除取决于切变速度及湍流强度以外,还是烟流半径的函数,因而在物理上更加合理.由联合作用模式导出的终极抬升公式比不考虑环境湍流累积作用的公式更符合观测结果.
农村义务教育公平指标体系研究——基于湖北省武穴市农村调查
Research on Rural Compulsory Education Equity Index System——Take Wuxue City in Hubei Province as Example

,朱国华
- , 2015,
Abstract: 当前的教育公平指标体系研究很少涉足农村义务教育领域,且其构建存在重量轻质、数据来源单一以及理论依据非本土化的问题,因此有必要深入农民生活实际寻找公平指标,对教育公平指标体系进行重构。基于扎根理论对湖北省武穴市农民进行深入访谈,得到了衡量教育公平的指标;依据这些指标,运用层次分析法,建立了农村义务教育公平指标体系,并利用模糊综合评价进行了实证检验,得到农村义务教育公平整体现状,为资源的合理有效配置提供了有效的参考工具。
The research on the current equity index system,scarcely associated with the sphere of rural compulsory education,attaches too much importance to quantity research other than quality research,and is deeply haunted with the problems of sole data sources and non-localized theoretical basis.So it is necessary to search for the educational equity indicator in peasants’ real life and reconstruct the system.Based on the in-depth interviews to peasants in rural areas in Wuxue City,Hubei province,this paper explored the educational equity indicators.Based on the indicators and AHP,the rural compulsory education fairness index system could be built.This paper further testified the system by the method of fuzzy comprehensive evaluation and obtained an overall condition of current rural compulsory education equity,thus providing effective references for the reasonable and effective allocation of educational resources.
学前儿童面部表情标签与指认能力现状调查
Facial Emotion Identify and Label Ability in Preschool Children
 [PDF]

, 谭钧文, 叶萍, 蔡小燕
Advances in Psychology (AP) , 2015, DOI: 10.12677/AP.2015.56053
Abstract:
观察面部表情是用来判断一个人的情绪是最直观的方法。本次研究选取了48张面部表情图标,以学前儿童为被试,调查学前儿童的表情识别与标签的能力。在浙江省L市随机选取一所幼儿园,分别选取小、中、大班年段的幼儿各30名,一共90人,进行单独的表情识别和标签测试。基于数据分析得出以下结论:1) 学前儿童表情识别与标签能力发展最好的是高兴,其次是悲伤和愤怒,再次是惊讶、恐惧、厌恶。2) 女童在对儿童的面部表情图片进行标签任务时的表现显著优于男童(p < 0.05);3) 小班到大班阶段,学前儿童的表情识别与标签能力发展迅速,在表情识别的任务中大班的表现要优于小班的表现,并且差异十分显著(p < 0.001);4) 学前儿童在识别表情的任务表现中,白种人与中国人图片之间不存在显著差异,在标签任务与指认任务之间不存在显著差异。
The most intuitive approach to determine a person’s mood is observing the facial expression. This research investigated the ability to identify and label human facial emotions on preschool children. 90 preschool children were recruited from one kindergarten in L city in Zhejiang Province, 30 in junior class, 30 in middle and 30 in senior class. In this study, 48 facial expression images were selected as stimuli. The study results indicated: 1) the preschool children have perfect performance on identify and label happiness expression, followed by facial expression on sadness and anger, surprise, fear, disgust; 2) compared with boys, girls are performed significantly better than boys on label task (p < 0.05); 3) preschool children has rapid development on facial expression recognition and label, in all four facial expression recognition task, senior class performed better than junior class, and the difference is very significant (p < 0.001); 4) there is no significant difference between Caucasian and Chinese picture, and there is no significant differences between identifying task and labeling task in the performance on preschool children.
Globus-Based Grid Replica Location
基于Globus平台的网格副本创建

丽君,
计算机系统应用 , 2008,
Abstract: 为了分析不同网格副本创建策略的性能,根据基于Globus平台的网格副本结构,通过实验比较了三种策略的指标,体现了策略创建的多样性,为具体的访问需求提供副本创建参考。本次实验证明策略的正确与否很大程度上决定了网格的性能高低,而策略创建的多样性则表明了该项研究的任重道远。
城市大气污染源排污负荷优化分配模型
王勤耕,
环境科学学报 , 1996,
Abstract: 排污负荷分配到源是进行大气污染总量控制的一个基本原则。应用数学规划的方法进行排污负荷分配研究,可以得到区域总体优化的分配方案。通常的线性规划模型在进行该项研究时,存在规划排污量“极端化”的现象,即绝大多数的污染源要么以下界排放,要么以上界排放。这常常不能很好地符合实际工作的需要,引入硬边界约束和软边界约束,很好地解决了这个问题,使得排污负荷分配方案既不失总体优化特征,又能更好地符合实际。
MARC四十年的发展及其未来
胡小菁,
中国图书馆学报 , 2010,
Abstract: MARC问世至今已有40年,图书馆资源委员会与艾弗拉姆的贡献至关重要。MARC首创元数据标识系统,采用纯文本文件,开发过程中吸收他馆经验并进行编目工作流程成本分析,提供了实用的产品,因而长盛不衰。MARC问世后,国际图联(IFLA)和各国相继开发了UNIMARC和本国MARC,20世纪90年代后出现转向USMARC/MARC21的趋势,XML格式的MARC成为新的方向。未来MARC将包含更丰富的信息,直接利用外部数据并结合FRBR,最终有可能回归书目数据的交换格式。参考文献26。
黄脸油葫芦的鸣声结构及行为分析(直翅目:蟋蟀总科)
何祝清,
华东师范大学学报(自然科学版) , 2009,
Abstract: 研究了黄脸油葫芦Teleogryllusemma(OhmachiandMatsumura,1951)的多种行为模式,并对其鸣声结构进行了分析.其行为模式包括取食、清理、避敌、交配和鸣叫等,鸣声包括召唤声、求偶声和争斗声.鸣声时域特征结果表明黄脸油葫芦的鸣声一般由主音和陪音构成,召唤声和求偶声均具有主音和陪音,求偶声相对召唤声而言,陪音部分较长,而争斗声只具有主音部分;鸣声频域特征表明争斗声的频率高于其他两类鸣声的频率.
北京大学公共体育课程改革方案的启示与思考
杰?,何仲
天津体育学院学报 , 2007,
Abstract:
基于拥堵概率的城市快速路入口匝道控制策略
嘉,
- , 2017,
Abstract: 为解决城市快速路交通拥挤问题,开展快速路入口匝道控制策略研究.采用现行规范与现场数据建立VISSIM微观仿真模型,基于交通仿真分析,建立快速路入口合流区的拥堵概率模型,提出基于拥堵概率的入口匝道控制策略.通过收集主线上游流量以及入口匝道流量,预测拥堵概率;若拥堵概率超过其临界值,则启用入口匝道控制系统,确定匝道入口调节率和信号周期.研究表明,相比无信号控制,基于拥堵概率的快速路入口匝道控制策略能够使拥堵概率降至0.1左右,主线车速提高约20%.
To release and solve traffic jam on expressway, it is necessary to investigate the ramp metering strategy of expressway. Current specification and field data were used to build the VISSIM simulation model. The breakdown probability models of expressway ramp were established by microscopic traffic simulation, and a ramp metering strategy based on breakdown probability model was put forward. According to the mainstream and ramp volume, the breakdown probability was predicted. If the probability is higher than the threshold, the metering system turns on, and the on-ramp metering rate and cycle time are calculated. Compared with a ramp without metering strategy, the breakdown probability reduced to about 0.1, while the speed of mainstream increased by about 20 %.
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