利用酶催化交联提高纸板湿强度

木素-碳水化合物复合体（Lignin-Carbohydrate Complexes,简称LCC）是植物细胞壁的重要组成部分,木素和碳水化合物之间的交联赋予了木材和植物茎杆的物理强度和抗生物降解性能。但是,制成纸浆后,其大部分LCC和细胞壁不再存在,重新交织形成的纸板的强度远远低于原本木材和植物茎杆的强度,尤其是湿强度方面。通过在纸板中模拟生物合成LCC的方法,在一定程度上使得纸板中的纤维之间产生类似于细胞壁的复合物,实现植物纤维细胞的胞间层的修复,从而一定程度的提高纸张的物理强度（尤其是湿强度）。     

酶催化交联提高纸板湿强度的研究现状

木素-碳水化合物复合体(Lignin-Carbohydrate Complexes,简称LCC)是植物细胞壁的重要组成部分,木素和碳水化合物之间的交联赋予了木材和植物茎秆的物理强度和抗生物降解性能。但是,制成纸浆后,其大部分LCC和细胞壁不再存在,重新交织形成的纸板的强度远远低于原本木材和植物茎杆的强度,尤其是湿强度更低。通过在纸板中模拟生物合成LCC的方法,在一定程度上使得纸板中的纤维之间产生类似于细胞壁的复合物,实现植物纤维细胞的胞间层的修复,从而在一定程度上提高纸张的物理强度(尤其是湿强度)。     

基于双边LCC拓扑结构的无线充电系统集成线圈设计研究

双边LCC拓扑结构为电动汽车无线充电提供了一种高效的补偿方法,然而两个补偿线圈占据了很大的体积。为了解决电动汽车无线充电系统体积增大问题以及提高系统传输效率,文中提出了一种新型集成线圈的方法,将双极性补偿线圈集成到单极性主线圈中,利用3D有限元分析工具ANSYS Maxwell对新型电磁耦合机构进行优化,通过优化补偿线圈的长宽比来消除系统中的多余耦合系数,从而提高系统的传输效率。通过实验结果表明,采用该集成线圈方法的无线充电系统受两侧线圈的水平或垂直方向偏移的影响较小,此时系统传输效率较高。     

External uncertainty factors and LCC: a case study

Life cycle cost (LCC) is a significant consideration in any decision-making process. Although a body of knowledge exists on LCC in construction, little exists on the uncertainties during the operational period. A case study of French high-rise social housing is examined to identify some factors causing uncertainty. The historical data from these buildings are analysed to estimate the impact of some external factors (functional changes, technological changes, and regulatory changes) on the life cycle cost. New formulae for integrating this impact into the calculation of LCC are proposed and cost indicators are suggested for the LCC evaluation of similar buildings. The findings are a step towards a higher level of reliability in LCC evaluation taking account of some usually unexpected uncertainty factors.

Le coût du cycle de vie (CCV) est un facteur important à prendre en considération dans tout processus de prise de décision. Bien qu'un corpus de connaissances existe sur le CCV dans l'industrie du bâtiment, il y a peu de choses sur les incertitudes pendant la période d'exploitation. Une étude de cas sur le logement social dans les grands ensembles français est examinée afin d'identifier certains facteurs qui sont sources d'incertitude. Les données historiques provenant de ces immeubles sont analysées afin d'estimer l'impact de certains facteurs extérieurs (changements fonctionnels, changements technologiques et changements réglementaires) sur le coût du cycle de vie. De nouvelles formules permettant d'intégrer cet impact dans le calcul du CCV sont proposées et il est suggéré des indicateurs de coût pour l'évaluation du CCV d'immeubles similaires. Les résultats constituent un pas vers un niveau accru de fiabilité dans l'évaluation du CCV, tenant compte de certains facteurs d'incertitude généralement imprévus.

Mots clés: gestion d'actifs, entretien d'immeubles, gestion globale de bâtiments, logement, coût du cycle de vie (CCV), durée, incertitude     

特高压混合级联多端直流输电系统的协调控制策略研究

逆变侧采用电网换相换流器(LCC)和模块化多电平换流器(MMC)串联组成的特高压混合级联多端直流输电系统,为特高压直流输电提供了一种更为经济、灵活、快捷的输电方式。基于现有直流电网的协调控制策略,文中对受端MMC阀组之间的协调控制策略进行了深入的分析研究,并考虑了5种协调控制策略。然后,在PSCAD/EMTDC中,对上述5种策略遭受不同故障的响应特性分别进行仿真,故障包括送端交流故障、直流线路故障、受端LCC交流故障、受端MMC1交流故障及MMC1紧急闭锁退出。最后,基于仿真结果,对上述5种协调控制策略的适用性进行了对比分析。仿真结果表明:策略1和策略3遭受各种故障均能有效穿越;策略2、策略4和策略5在遭受直流线路故障时均发生不同程度的功率倒转,需要采取措施抑制。     

LC串联谐振和LCC串并联谐振在高压脉冲电容充电电源中的应用比较

为得到更适合高压脉冲电容充电电源的电路拓扑,对LC串联谐振和LCC串并联谐振充电电源的应用电路特性进行了比较。利用Matlab分别对LC串联谐振和LCC串并联谐振脉冲电容充电电路进行了仿真分析,通过3kW电源样机对600μF/15kV负载电容进行了充电实验,给出了LCC串并联谐振实验波形,与仿真结果一致。实验结果说明实际LC串联谐振电路由于分布电容的影响变为LCC串并联谐振,并根据附加并联电容对电路分布电容的大小进行了间接测量,LCC串并联谐振所需供电电源功率较小、电流峰值较低、充电精度较高,因而更具优越性。     

大功率ESP高频高压电源

针对静电除尘用工频电源存在缺陷,设计了一种静电除尘用高频开关电源,分析了各开关模态,采用基波近似法对LCC谐振变换器进行了分析,并用saber软件进行了仿真验证.仿真结果表明,控制频率与输出电压之间的关系具有非线性特点,越接近谐振频率,这种非线性越明显;电路开始谐振的阶段,谐振电路有明显的电流冲击,这可能会对主回路中的器件特别是IGBT产生较大电流应力.     

Life cycle environmental and economic analyses of a hydrogen station with wind energy

This study aimed to identify the environmental and economic aspects of the wind-hydrogen system using life cycle assessment (LCA) and life cycle costing (LCC) methodologies. The target H₂ pathways are the H₂ pathway of water electrolysis (WE) with wind power (WE[Wind]) and the H₂ pathway of WE by Korean electricity mix (WE[KEM]). Conventional fuels (gasoline and diesel) are also included as target fuel pathways to identify the fuel pathways with economic and environmental advantages over conventional fuels. The key environmental issues in the transportation sector are analyzed in terms of fossil fuel consumption (FFC), regulated air pollutants (RAPs), abiotic resource depletion (ARD), and global warming (GW). The life cycle costs of the target fuel pathways consist of the well-to-tank (WTT) costs and the tank-to-wheel (TTW) costs. Moreover, two scenarios are analyzed to predict potential economic and environmental improvements offered by wind energy-powered hydrogen stations.     

受端混联LCC-VSC特高压直流输电系统故障穿越方法

针对受端由电网换相换流器（LCC）和电压源换流器（VSC）级联的混合直流输电系统中VSC在交流故障穿越时子模块过压的问题,文中提出在受端VSC直流侧安装耗能设备以抑制VSC子模块过压的方法,对比分析了基于直流斩波耗能电阻、泄流晶闸管和可控避雷器3种耗能设备的交流故障穿越原理及策略。基于PSCAD/EMTDC仿真平台搭建了包含工程实际控制保护主机程序的受端混联LCC-VSC特高压直流仿真模型,对比分析了3种耗能设备的交流系统故障穿越特性,结果表明在受端VSC直流侧安装耗能设备可以有效抑制子模块过压,实现交流故障可靠穿越。其中可控避雷器方案具有控制原理简单、可靠性高等优点,更适用于受端混联LCC-VSC特高压直流输电系统。     

Uncertainties related to financial variables within infrastructure life cycle costing: a literature review

Life cycle costing (LCC) is commonly undertaken deterministically, even though uncertainty is acknowledged to be present and acknowledged that it should be incorporated. However, no systematic review has been undertaken to explore how uncertainty might be dealt with in LCC. This paper reviews different approaches that acknowledge uncertainty within LCC, and in particular how such approaches treat uncertainty in the underlying financial variables of cash flows, interest rates, timing of cash flows, and LCC analysis duration. The approaches are categorised according to the use of, for example, frequency and probability distributions, fuzzy sets, moments, Markov chains, Bayesian thinking, artificial neural networks, pedigree matrices and composite and specialist approaches to characterise the variables. It is seen that: the most commonly used approaches for dealing with uncertainty in all LCC financial variables are probability distributions and fuzzy sets; some approaches are seen to be specific to one financial variable – the mechanistic-empirical approach for the timing of cash flows, and the gamma process for the duration; while two financial variables, namely cash flows and interest rates, attract the most attention from researchers. With no existing reviews solely exploring uncertainty within LCC or dealing with uncertainty in a systematic way, the paper fills a knowledge gap. The paper will be of interest to those involved with infrastructure LCC.