Positive set‐operators of low complexity

The powerset operator, ??, is compared with other operators of similar type and logical complexity. Namely we examine positive operators whose defining formula has a canonical form containing at most a string of universal quantifiers. We call them ?‐operators. The question we address in this paper is: How is the class of ?‐operators generated ? It is shown that every positive ?‐operator Γ such that Γ(??) ≠ ??, is finitely generated from ??, the identity operator Id, constant operators and certain trivial ones by composition, ∪ and ∩. This extends results of [3] concerning bounded positive operators.     

嵌入式IPv6协议的设计与实现

随着联网设备特别是嵌入式联网设备数量的增加,能提供几乎无穷尽IP地址的IPv6协议的优势越来越显著.所以,在嵌入式设备中实现IPv6协议栈具有很大的现实意义.结合嵌入式本身所固有的性质,给出了IPv6的设计原则和关键技术.实现时简化了IPv6模块中的ICMPv6和邻居发现的相关功能,在传输层只实现TCP模块,并简化了TCP运行状态机机制.最后将实现的协议通过移植到LPC2200开发板上,并通过简单C/S通信实验表明协议实现的可行性.整个软件代码量小、结构简单、易于移植和扩充.对嵌入式设备上移植IPv6协议栈提供了参考方案.     

EasyARM2200在吊装机械状态监控系统中的应用研究

采用嵌入式微处理器开发板EasyARM2200设计了大型吊装机械状态监控系统的硬件,给出了软件组成和程序流程图。将采用三个热释电传感器实现的人员定位及其算法引入该系统,可有效防止人员的意外伤害。系统的各项指标均满足设计要求,具有较强的可移植性,能方便地嵌入到其他嵌入式系统产品的设计中,可大大缩短开发周期。     

基于TCP／IP的单片机数据传输设计

研究利用了TCP／IP协议实现了低成本的8住单片机的以太网数据传输．以Atmegal6单片机和CP2200网络芯片为硬件平台,对TCP／IP协议簇进行精简,设计并实现了一个智能家电网络数据传输的精简TCP／IP协议,实现了ARP、ICMP、IP、UDP协议模块．通过多项实验对数据传输的正确性进行了验证．具有成本低、易使用、可移植性强的特点．     

Abrupt climate change and collapse of ancient civilizations at 2200BC-2000BC

Plentiful evidence of historical, archaeological and palaeoclimatic studies proved that an abrupt change from wetter to drier climate occurred over the Nile Valley, the Mesopotamia, the Indus Valley and Huanghe River Valley at 2200BC-2000BC. The abrupt change was developed based on the general lowering of temperature in the middle latitudes, and was a strong cold event since the beginning of the Megathermal (8.5-3.0 kaBP). Collapse of Nile civilization appeared at the First Intermediate Period (2181BC-2040BC). Civilization of Mesopotamia began collapse following the disintegration of Akkadian Empire. This process lasted to the foundation of Babylon Kingdom from 2200BC to 1900BC. Indus civilization abruptly fell off at 1800BC. A widespread alternation of archaeological cultures happened in China at ca. 2000BC except only in its central part. Longsheng culture was replaced by the Erlitou culture, which is now acknowledged in China as Xia Culture. Foundation of Xia Dynasty at 2070BC opened a new chapter in the development of Chinese civilization. Studies indicated that abrupt climate change may be caused by the weakening of the Thermohaline Circulation (THC).     

基于LME2200智能家庭系统的研究

本文提出了以是一款由Samsung公司生产的S3C2410为核心处理器、基于电力线调制解调器LME2200的智能家居的总体方案,此方案的控制方式多样,使我们家庭成为协调一致的自动化智能化系统。     

2200—2000BC的气候突变与古文明的衰落

综合分析了历史学、考古学及古气候学的证据.证明2200-2000 BC在尼罗河流域、两河流域、印度河流域及黄河流域均发生了向干旱转变的气候突变.这次突变以中纬度普遍的变冷为背景,是全新世进入大暖期以来的一次强冷事件.尼罗河文明的衰落发生于第一中间期(2181-2040 BC),两河流域文明的衰落从阿卡德王国解体开始,到古巴比伦王国建立为止,约2200-1900 BC.印度河文明于1800 BC突然衰落.2000 BC前后中华文明在中原以外有广泛的交替,而中原龙山文化演变为二里头文化.2070 BC建立了夏朝,揭开了中华文明的纪元.研究表明,热盐环流(THC)的变化可能是气候突变的直接原因.