Beyond the LAN: Ethernet’s Evolution into the Public Network

This article details the evolution of Ethernet into Gigabit Ethernet and how this LAN-based technology has undergone major transformations over time. From its data rates and distances to supported media and functionality, Ethernet has greatly improved, enabling it to surmount many of its former limitations and in so doing to expand beyond the LAN into the MAN and now even the WAN. In this article, Pioneer Consulting explores the evolution further by focusing on some of the major technological directions in the Ethernet equipment industry.     

Independent particle model of spontaneous symmetry breaking in planar π-electron systems

The singlet stability of symmetry adapted (SA), restricted Hartree-Fock (RHF) solutions, and the implied symmetry breaking for several planar, π-electron systems, is investigated using the semiempirical Pariser-Parr-Pople Hamiltonian in the whole range of the coupling constant. We focus here on highly symmetric cyclic polyenes C₁₀H₁₀ and C₁₄H₁₄ and their various distorted analogues of lower symmetry, in particular on the perimeter models of naphthalene and anthracene (p-naphthalene and p-anthracene) modeling the so-called [n]-annulenes. Relying on earlier results for general systems with conjugated double-bonds, we explore the character and properties of both the SA and broken-symmetry (BS) RHF solutions for these systems and relate their behavior to those of highly symmetric cyclic polyenes and corresponding polyacenes. In this way we are able to provide a better understanding of the spontaneous symmetry breaking in these systems at the Hartree-Fock level of approximation.     

Transition probabilities of forbidden lines in Pb I

Multiconfiguration Dirac-Fock as well as semiempirical calculations of decay rates of forbidden transitions within the ground 6s ² 6p ² configuration of neutral lead are reported and compared with relativistic Hartree-Fock results as well as with available experimental data. Received: 15 July 1998 / Received in final form: 15 October 1998     

PPP项目中国有企业与民营企业的融资效率对比研究

目前PPP模式的应用范围不断扩大,但投资者的融资效率普遍不高。投资者融资效率低下严重影响PPP项目绩效,制约PPP模式的可持续发展。本文以51家主营业务为PPP项目的国有企业与民营企业为样本,运用DEA模型分别从整体、不同领域和不同地区之间对比分析双方融资效率的异同。结果显示参与PPP项目投资者的规模效率普遍不足,主营成本与股权集中度是导致融资效率低下的主要因素,净资产收益率较低则是投资者不愿积极参与PPP项目的一个主要原因。对国企而言,优化企业对PPP项目的规模效率是提高融资效率的关键;而民企应注重优化和降低资产负债率,合理均衡地分配股权。因此,建议具有规模效率和纯技术效率优势的投资者通过组建联合体等方式参与PPP项目,实现优势互补,从而提高项目公司的整体效率。此外,也要针对不同领域和不同地区PPP项目的特点和对投资者的要求,有针对性地选择投资者,充分发挥国企资金实力雄厚和民企专业技术的优势,提高融资效率,助力PPP实践的可持续发展。     

基于或有可换债的PPP项目资本证券化研究

PPP项目具有的“大而不倒”特性,致使其陷入财务困境时,政府不得不介入和对其进行救助。然而这种救助必然会扭曲PPP项目定价和加剧市场的不正当竞争。为对冲PPP项目资本短缺的风险及抑制项目“大而不倒”负面效应,建议社会资本方发行或有可换债(CEBs)。CEBs在可换债的基础上引入或有可转债的条款,使其具有危机救助功能和风险转移功能。且CEBs的发行不会增加项目运营公司的公司债务。只有当项目因资本短缺而陷入财务困境时,社会资本方可以通过CEBs转为项目特定收益权和债务减记的方式来增加可支配资本,以维持PPP项目正常运营。研究表明,CEBs通过类似保险的形式对冲项目的资本短缺的风险;为社会资本提供合理的退出机制;对冲政府的裸露头寸。     

PPP项目建造和营运的治理模式选择研究

PPP模式在中国情境下实施、建造和营运环节的治理和协调是一个十分重要的问题。基于交易费用经济学和新产权理论,建立数学模型,对PPP模式的治理展开探讨。首先建立了PPP项目的一般治理模式的数学模型,分析了最优社会福利,然后针对需求风险偿付契约分别建立了PPP项目的建造、营运分立治理模型和建造、营运合一的治理模型。研究表明:在需求风险偿付契约下,建、营合一治理模式比建、营分立的治理模式具有更高的社会福利。     

有机试剂结构与性质的研究(X)——偶氮苯衍生物结构与吸收光谱的研究

本文应用PPP-SCF-CI法计算了偶氮苯衍生物的结构,发现偶氮苯衍生物波长最大的吸收峰(相应于电子从基态向第一激发态跃迁)是分子内荷移光谱,这些吸收峰的计算值与实验值完全一致.此外,还根据PPP计算结果研究了取代基对吸收光谱的影响.