125kHz射频识别阅读器模块的设计与实现

设计了一个工作频率为125kHz低频射频识别阅读器的通用模块。设计方案中采用Atmel公司的基站芯片U2270b与Silion Labo-ratory公司的C8051微控制芯片配合工作,完成了射频载波信号的产生、放大、调制、解调与解码功能。文中介绍了硬件的工作原理、模块组成、解码程序的设计方法,并给出了相关设计文档与实物结果。通过软硬件调试与测试,获得了准确的解码时序,最终实现了对EM4100各类型兼容ID卡的正确识别。     

冷战后新保守主义影响美国对华政策的手段

美国新保守主义的外交思想及政策具有浓厚的意识形态色彩和强烈的进攻性。冷战后,新保守主义者仍然奉行冷战思维,鼓吹"中国威胁论",主张对华奉行强硬的"遏制政策"。他们通过参与政治实践、操纵媒体引导舆论、控制国会影响立法等手段,影响克林顿、布什政府的对华政策,使布什政府的对华政策具有明显的新保守主义特征。     

Differential commutator identities

I.N. Herstein proved that if R is a prime ring satisfying a differential identity , with d a nonzero derivation of R, then R embeds isomorphically in M₂(F) for F a field. We consider a natural generalization of this result for the class of polynomials E_n(X)=[E_n-1(x₁,…,x_n-1),x_n]. Using matrix computations, we prove that if R satisfies a differential identity , or with some restrictions, then R must embed in M₂(F), but that differential identities using [[E_n,E_m],E_s] with m,n,s>1 need not force R to embed in M₂(F). These results hold if the expressions are identities for a noncommutative Lie ideal of R, rather than for R itself.     

Kinetics, thermodynamics and surface heterogeneity assessment of uranium(VI) adsorption onto cation exchange resin derived from a lignocellulosic residue

A new cation exchange resin (PGTFS-COOH) having a carboxylate functional group at the chain end was prepared by grafting poly(hydroxyethylmethacrylate) onto tamarind fruit shell, TFS (a lignocellulosic residue) using potassium peroxydisulphate-sodium thiosulphate redox initiator, and in the presence of N,N′-methylenebisacrylamide (MBA) as a crosslinking agent, followed by functionalisation. The adsorbent was characterized with the help of FTIR, XRD, scanning electron micrographs (SEM), and potentiometric titrations. The kinetic and isotherm data, obtained at optimum pH value 6.0 at different temperatures could be fitted with pseudo-second-order equation and Sips isotherm model, respectively. An increase in temperature induces positive effect on the adsorption process. The calculated activation energy of adsorption (E_a, 18.67 kJ/mol) indicates that U(VI) adsorption was largely due to diffusion-controlled process. The values of adsorption enthalpy, Gibbs free energy, and entropy were calculated using thermodynamic function relationships. The decrease in adsorption enthalpy with increasing U(VI) uploading on the adsorbent, reflects the surface energetic heterogeneity of the adsorbent. The isosteric heat of adsorption was quantitatively correlated with the fractional loading for the U(VI) ions adsorption onto PGTFS-COOH. The results showed that the PGTFS-COOH possessed heterogeneous surface with sorption sites having different activities.     

在美国破产保护法第十一章下公司债券的定价和最佳破产边界研究

为了更好地处理公司破产重组问题,综合采用结构化方法和最优停时技巧,基于美国破产保护法第十一章,分析了有限到期日公司债券的定价问题,本质上为最优停时问题.用偏微分方程法证明了最佳破产边界的存在唯一性和单调性,得到了公司策略债务支付息票的显式表达式.数值结果表明：在美国破产保护法第十一章下,公司的破产率更高,股东可通过提前宣布破产而获益,而债权人能否获益依赖于谈判因子和谈判费用.     

An ensemble of idempotent lifting hypotheses

Lifting idempotents modulo ideals is an important tool in studying the structure of rings. This paper lays out the consequences of lifting other properties modulo ideals, including lifting of von Neumann regular elements, lifting isomorphic idempotents, and lifting conjugate idempotents. Applications are given for IC rings, perspective rings, and Dedekind-finite rings, which improve multiple results in the literature. We give a new characterization of the class of exchange rings; they are rings where regular elements lift modulo all left ideals.We also uncover some hidden connections between these lifting properties. For instance, if regular elements lift modulo an ideal, then so do isomorphic idempotents. The converse is true when units lift. The logical relationships between these and several other important lifting properties are completely characterized. Along the way, multiple examples are developed that illustrate limitations to the theory.     

p-超循环嵌入子群的一个判别准则

令E是有限群G的一个正规子群,且U是所有有限超可解群的集合.E称为在G中是p-超循环嵌入的,如果E的每个pd-阶的G-主因子是循环的.G的子群H称为在G中是U-Φ-可补充的,如果存在G的一个次正规子群T,使得G=HT,且(H∩T)H_G/H_G≤Φ/(H/H_G)Z_U(G/H_G),其中Z_U(G/H_G)是商群G/H_G的U-超中心.作者证明,如果E的一些p-子群在G中是U-Φ-可补充的,那么E在G中是p-超循环嵌入的.作为应用,得到了有限群是p-超可解的若干判断准则,并且推广了一些已知的结果.     

碳排放对绿色全要素生产率的影响与地区异质效应

采用DEA-Malmquist方法测度绿色全要素生产率,构建1998-2017年中国省际面板数据模型,考察碳排放对绿色全要素生产率的影响,并进一步分析其地区异质效应.结果表明：碳排放与绿色全要素生产率之间存在显著的倒U型关系,即具有先促进后抑制的作用;碳排放对绿色全要素生产率的影响存在显著的地区异质性,其中,在东部和中部地区呈现出显著的促进作用,而对西部地区则存在显著的倒U型关系.     

Invariant currents and dynamical Lelong numbers

Let ƒ be a polynomial automorphism of ℂ^k of degree λ, whose rational extension to ℙ^k maps the hyperplane at infinity to a single point. Given any positive closed current S on ℙ^k of bidegree (1,1), we show that the sequence λ⁻ⁿ(ƒⁿ)*S converges in the sense of currents on ℙ^k to a linear combination of the Green current T₊ of ƒ and the current of integration along the hyperplane at infinity. We give an interpretation of the coefficients in terms of generalized Lelong numbers with respect to an invariant dynamical current for ƒ⁻¹.