检测水中耗氧量影响因素的探讨

文章从加热时间、加热温度、滴定温度、K值等方面,利用正交试验和验证实验来探讨水中耗氧量检测时各因素的主次关系,从而优化实验条件,提高检测结果的准确度。实验表明:加热时间对耗氧量的影响因素最大,第二为加热温度,第三为K值,影响最低的为滴定温度。水中耗氧量检测时,加热温度应95℃,加热时间为32 min,k值控制在0.96~1.04。     

水中桥墩施工实用工艺初探

市政工程施工中,现场条件复杂多变。通过工程实例介绍一种简单实用的水中桥墩施工工艺,对桥梁关键工序水下施工,如何既保证质量又节约成本作了有益尝试。对类似工程施工有借鉴作用。     

北京音乐厅改建工程空调消声系统设计

随着国家文化产业的发展,音乐厅、剧场等文化建筑越来越受到重视。本文针对音乐厅对音质、背景噪声等的特殊要求,对空调系统的气流组织形式、消声、减振、隔振方案进行了阐述,指出了噪声控制应从机房布置、噪声源、传声途径、音乐厅内部吸声四个方面进行综合处理。最后通过对北京音乐厅改造后室内噪声的实际测量结果,对设计方案予以认证。     

Antiproliferative and antioxidant properties of anthocyanin-rich extract from açai

An anthocyanin-rich extract, generated from açai (AEA), was investigated for its antioxidant properties and antiproliferative activity against C-6 rat brain glioma cells and MDA-468 human breast cancer cells. AEA has an ORAC value of 2589 μmoles trolox equivalents (TE)/g dried powder and a DPPH radical-scavenging activity of 1208 μmoles TE/g, suggesting that AEA is an exceptional source of natural antioxidants. In addition, AEA remarkably suppresses proliferation of C-6 rat brain glioma cells, but has no effect on the growth of MDA-468 human breast cancer cells. Further experiments demonstrated that the AEA treatment dose-dependently inhibited the growth of C-6 rat glioma cells with an IC₅₀ of 121 μg/ml. The DNA ladder fragmentation results indicated that AEA induced apoptosis of C-6 rat brain glioma cells. To compare açai with other anthocyanin-rich extracts, a number of berry extracts, including blueberry, strawberry, raspberry, blackberry and wolfberry, were assessed for potential antiproliferative activity against C-6 rat brain glioma cells. However, none of them showed suppressing effect. The results suggest that the active antiproliferative constituents in AEA are unlikely to be anthocyanins normally found in common berries.     

战斗机高空综合环境模拟舱压カ控制策略研究

高空综合环境模拟舱能够实现高空温度、压力和湿度等参数模拟，对军用战斗机环控系统研究具有重要意义。在多参数综合模拟试验时，传统的试验方法和控制策略不能很好地实现压力与其它环境参数的解耦控制，造成无法快速准确地实现多综合参数模拟。为此，提出单独采用抽气阀控制环境舱压力的试验方法，结合提出的基于非线性补偿的二自由度PID压力控制策略快速控制舱内高度。该控制策略引入非线性补偿环节克服抽气阀的非线性流量特征，同时引入二自由度PID克服压力超调，提高压力调节速度。新的试验方法和压力控制策略为实现多环境参数解耦控制提供了保证，同时能提高模拟舱内无超调压力控制精度和响应速度。该压力控制篥略同样适用于其它压力控制场合。     

Juice matrix composition and ascorbic acid fortification effects on the phytochemical,antioxidant and pigment stability of açai (Euterpe oleracea Mart.)

The effects of juice matrix composition on the phytochemical stability of açai (Euterpe oleracea Mart.) were evaluated by contrasting natural clarified juice systems with isolated polyphenolic and anthocyanin fractions, in the presence or absence of ascorbic acid (500 mg/l) under accelerated storage conditions (37 °C). Polyphenolic (anthocyanin and non-anthocyanin polyphenolics) and anthocyanin fractions were isolated using C18 Sep-Pak columns and then re-dissolved in the original aqueous juice matrix (unbound fraction) or in a citric acid buffer (pH 3.5). The isolation of anthocyanins from the açai matrix improved their colour stability but a greater retention of non-anthocyanin polyphenolics and antioxidant properties was favoured by the initial juice composition. The presence of non-anthocyanin polyphenolics exerted a protective effect against ascorbic acid oxidation and enhanced polyphenolic and antioxidant stability in isolates fortified with ascorbic acid. However, all isolates obtained from açai experienced significant colour, polyphenolic, and antioxidant losses during storage and this indicated that optimization of early stages of industrial processing, storage and distribution are necessary to retain the functional properties of açai-containing products.     

转子系统中的非线性时间序列预测

针对转子系统中出现的非线性信号 ,提出了一种基于吸引子的自适应预测方法。实验结果表明 ,和其他预测方法相比 ,该方法具有更高的精度。     

原木板材的窑式干燥

本文综述了canterbury大学近年来关于新西兰木材窑式干燥的研究。有些硬木单纯窑式干燥是困难的,但利用太阳能窑式风干则有可能;轮回操作可以减小干燥应力从而减小产品性能的退化程度。种植生产为主的软木干燥较容易,从经济考虑应采用高温干燥,以减少干燥时间。高温操作时对流传递显得相当重要。实验表明,当空气流过板面时,不同点处的传质系数有显著差异。湿分在木板中移动的模型可假定为:随着干燥进行蒸发面向中心退缩。但心材和边材的行为有所不同:边材中的水份可在相邻脉管间迁移,但在心材中则不可能。正是这种差异导致干燥时间和干燥温度曲线不同。     

火电厂的实时状态监测系统与故障诊断

针对国内大多数火电厂现场设备控制的现状,提出一个经济型实时状态监测系统方案,在充分利用原有设备的前提下,采用集散控制系统（ＤＣＳ）结构和ＦＩＸ组态软件实现某厂各主要站点的集中监视和统一管理。在此基础上,利用实时状态数据对主要设备运行状态进行评估,对设备故障进行预测和诊断。现场运行结果表明：该系统对火电厂的现场设备实现了有效的集中监视,并可对主要设备进行故障预测和初步诊断。