溴化锂制冷机溶液除铜技术

提出了一种能有效去除废旧LiBr溶液中铜杂质的方法.采用添加硫化钡并用稀HBr调节溶液的pH值和添加一种活性炭--硅藻土复合添加剂,通过搅拌、沉降、过滤,可使杂质铜的含量由原来的1200mg/L降至2～4mg/L,符合溴化锂制冷机(吸收式空调)国家标准关于LiBr溶液中铜含量的要求.     

A stellar relic from the early Milky Way

The chemical composition of the most metal-deficient stars largely reflects the composition of the gas from which they formed. These old stars provide crucial clues to the star formation history and the synthesis of chemical elements in the early Universe. They are the local relics of epochs otherwise observable only at very high redshifts; if totally metal-free ('population III') stars could be found, this would allow the direct study of the pristine gas from the Big Bang. Earlier searches for such stars found none with an iron abundance less than 1/10,000 that of the Sun, leading to the suggestion that low-mass stars could form from clouds above a critical iron abundance. Here we report the discovery of a low-mass star with an iron abundance as low as 1/200,000 of the solar value. This discovery suggests that population III stars could still exist--that is, that the first generation of stars also contained long-lived low-mass objects. The previous failure to find them may be an observational selection effect.     

Maligranda公开问题的一个解(英文)

Maligranda提出:若Φ是一N-函数,何时1/Φ-1(1/t)是一个凹函数?我们给出一个解.     

一种选择最优copula的新方法

传统的选择最优copula的方法大都是基于拟合优度的.引入了一种Bayes方法,这种方法独立于参数,通过计算各种copula类对应的概率来选择最优copula类.并选择上证指数和标准普尔500指数做实证分析,结果表明:与其他copula类相比,Clayton copula类对数据具有更好的拟合效果,进而得到指数间的下尾相关系数.     

A palaeontological solution to the arthropod head problem

The composition of the arthropod head has been one of the most controversial topics in zoology, with a large number of theories being proposed to account for it over the last century. Although fossils have been recognized as being of potential importance in resolving the issue, a lack of consensus over their systematics has obscured their contribution. Here, I show that a group of previously problematic Cambrian arthropods from the Burgess Shale and Chengjiang faunas form a clade close to crown-group euarthropods, the group containing myriapods, chelicerates, insects and crustaceans. They are characterized by modified or even absent endopods, and two pre-oral appendages. Comparison with reconstructions of the crown-group euarthropod ground plan and recent investigations into onychophorans demonstrates that these two appendages are the first antenna (of extant crustaceans) and a more anterior appendage associated with an ocular segment. The latter appendage has been reduced in all crown-group euarthropods. Its most likely relic is as a component of the labrum. These fossils thus tie together results from disparate living groups (onychophorans and euarthropods).     

A solution to the anonymity of the mobile subscriber

The user anonymity mechanism provided in GSM and UMTS network is analyzed,and a new approach to solve the anonymity of mobile subscriber is proposed in this paper.Using the ciphering algorithm with a dynamic key and a static key,the method allows mobile subscribers to connect network with user anonymity,and it can be seamlessly integrated with the existing authentication algorithms.The analyses reveal that the proposed scheme can provide the integrity protection of messages,prevent the replay attacks,and be implemented easily.     

Kortewey-de Vries方程的孤子解

利用一维波动方程行波解的形式，通过变量替换，再引入双曲正切函数作为独立变量并利用其独特的微分关系给变换，将Kortewey-de Vries方程简化为常微分方程，由此得出它的解。     

快速接入无线局域网解决方案

为顺应人们快速接入网络的要求,根据无线网络的工作原理以及用户对网络性能的要求,制定了采用CISCO设备实现快速接入无线局域网的一个解决方案,以此来达到移动的、稳定的、高速的、安全的接入网络.实验表明,此解决方案基本上可以满足当前的办公及家庭娱乐需求.     

连续型对称奇异线性控制系统的解

基于广义系统解的理论,通过矩阵的变换和矩阵的性质,讨论了连续型对称奇异线性控制系统的解的形式,并给出相关证明。     

Kortewey-de Vries方程的孤子解

利用一维波动方程行波解的形式,通过变量替换,再引入双曲正切函数作为独立变量并利用其独特的微分关系给变换,将Kortewey-de Vries方程简化为常微分方程,由此得出它的解.     

广义Williams问题的简单解法

继文 [1 ]研究广义 Williams问题 P( m,n,α,β,γ) =sin αmsin βmsin γn 的最大值 ,其中α,β,γ是某三角形的三内角 ,获得了统一的结果     

变形贝塞尔方程的新解法

本文定义了一对变形圆柱函数—混合柱函数,讨论了有关性质及渐近表达式。推导出变形贝塞尔方程边值问题的一般解及渐近解。最后讨论并定义了在涡流分析中要涉及的一个混合柱函数及其混合开耳芬函数。     

Ramsey数下界的一个新结果

Ramsey数是组合数学中很有意义的一个数[1],但确定Ramsey数的具体数值仍是一个尚未解决的问题,因此,给出Ramsey数尽可能小的上界和尽可能大的下界是有意义的。通过构造两个图的连结图,利用连结图的性质,得到求Ramsey数下界的一个新公式,利用该公式得到的Ramsey数的下界比其它公式得到的要好。     

提高风冷冷凝器换热能力的措施

处于通风不畅位置的风冷冷凝器,常由于进风中的新风量不足,大量排风重新被吸入,导致进风温度过高,冷凝器换热效果差,容易造成压缩机高压保护而停机．文章针对某工程机房空调的风冷冷水机组经常由于冷凝器换热条件差造成高压保护而停机的问题,经过数值模拟分析问题原因,提出了利用排风筒进行有组织排风的解决思路．实际改造结果证明该方案可...     

非线性分数阶Sharma-Tasso-Olver方程新的精确解

利用复变换和扩展的(G'/G)-展开法构建非线性分数阶Sharma-Tasso-Olver方程新的精确解,包括:双曲函数解、有理函数解和三角函数解.     

A molecular solution to the riddle of the giant panda's phylogeny

Although it is generally agreed that the giant panda (Ailuropoda melanoleuca) is a member of the order Carnivora, there has long been disagreement over whether it should be classified with bears, raccoons or as a single member of its own family. Four independent molecular and genetic measures lead to a consensus phylogeny for the giant and lesser pandas. The lesser panda diverged from New World procyonids at approximately the same time as their departure from ursids, while ancestors of the giant panda split from the ursid lineage much later, just before the radiation which led to modern bears. The giant panda's divergence was accompanied by a chromosomal reorganization which can be partially reconstructed from the ursid karyotype, but not from that of procyonids or the lesser panda. The apparently dramatic, but actually limited, distinctions between the giant panda and the bears in chromosomal and anatomical morphology provide a graphic mammalian example of the discordance of molecular and morphological (and chromosomal) evolutionary change.     

几何平均亚式期权定价模型的新解法

综合运用拉普拉斯变换和傅里叶变换,得到了具有固定敲定价的几何平均亚式期权定价模型的又一新解法.     

一般双曲面渐近锥面方程的一种简便求法

给出一般双曲面渐近锥面方程的一种新求法，与一般空间解析几何材料中所介绍的方法比较，显得非常简捷：