Influence of inoculum cell density and carbon dioxide concentration on fed-batch cultivation of Nannochloropsis oculata

The marine microalgae Nannochloropsis oculata is a promising source of biofuel because of its high lipid content. For achieving high productivity of oil from microalgae, a high cell concentration before harvesting is beneficial. The present study investigated fed-batch cultures of N. oculata fed with vitamins and nutrient solutions and found that the biomass yield of N. oculata in the fed-batch culture was 1.25 times higher than that in batch culture. Fed-batch cultivation, especially at high illumination, decreased the inhibitory effect of high carbon dioxide (CO₂) concentration on the microalgal growth. The specific growth rate was directly proportional to the light intensity in the CO₂ environment. A light intensity of 40,000 Lux was able to achieve high specific growth rates in fed-batch cultivation at a CO₂ volume fraction of 2%–15%. The tolerance of N. oculata to CO₂ was enhanced by the daily feeding of nutrients in the fed-batch cultivation. At 2% CO₂, a final cell density of about OD₆₈₂ = 11.4 was achieved in the fed-batch culture in 30 days. Furthermore, a cell density of 14.4 g L⁻¹ was obtained by outdoor fed-batch cultivation in 27 days.     

德国高速拉丝模之研究

德国ＨＥＲＫＥＬ公司生产的高速拉丝模具在高速拉拔粗规格、高强度预应力钢丝中表现出较长的使用寿命。用ＣＤＴ－２００拉丝模孔型微机检测仪对其剖析结果表明，该模具完全遵循＂直线型拉丝模＂孔型设计理论。     

速度,效率,环保：关于中国造纸工业持续发展的一些思考

本文探讨了在我国经济体制深入改革的新形势下，造纸工业发展的动力与主要制约因素，以及行业持续发展值得重视的一些问题。     

600MW汽轮机调速系统试验及辨识研究

以某电厂6号机组(600MW)为研究对象,为对其调速器系统模型参数进行辨识,设计并实施了相关的试验。在辨识过程中,针对常规参数辨识方法在进行汽轮机调速系统模型参数辨识时所遇到的困难,采用了一种基于遗传算法的模型参数辨识方法,并利用Matlab及其simulink工具箱予以实现。结果表明,该方法较为适用于汽轮机调速系统模型参数的辨识,辨识所得到的模型也达到了较高的仿真精度。     

Time stepping finite element analysis of a variable speed synchronous generator with rectifier

Several applications for renewable energy conversion make use of variable speed generators. A conversion from variable frequency to grid frequency is therefore essential. One part of the converter is a rectifier. A rectifier model is presented, which is integrated in a time stepping finite element simulation environment where the generator and circuit equations are solved simultaneously. The model handles bidirectional alternator speeds as the application is a linear generator for ocean wave energy conversion. The rectifier model is extended with a load model, consisting of R, L and E, and simulations show what impact the rectifier has on the generator’s behaviour.     

小樊一级站水泵出水量减少原因及改进方案分析

本文通过分析和计算得出,(1)水泵出水量减小的主原因是水泵随机资料有误;(2)提高泵站前池水位,增设32SA-19C型水泵是解决供水矛盾的有效措施;(3)加大24SA-18型水泵叶轮,可提高泵站运行的适应性与灵活性。     

NS100GA-5型铁路起重机制动系统的提速改造

通过对NS100GA-5型铁路起重机制动系统的提速改造,研制出一种适合于铁路起重机的制动系统。对其改造方案、具体结构和计算分析进行了阐述。经过动力学试验,证明该制动系统能够满足提速的要求。     

新型切割用燃气的工业应用概况

近年来,各种新型工业燃气已广泛应用于金属切割领域,本文介绍了各种新型工业燃气以及添加剂的应用概况,对其存在的问题及应用前景进行了展望。     

开关磁阻电机转速调节器参数模糊自整定的研究

开关磁阻电机(SRM)具有较强的非线性,很难建立其准确的数学模型,在传统PID调速控制中难以获得整个调速范围内Kp、KI、KD 3个参数的最优组合。而固定参数的传统PID调节器,不利于系统调速的精准性与抗干扰性。通过分析传统PID调节器3个参数的控制特点,主要针对起动、调速、负载扰动等若干状态下,建立适当的、通用的模糊控制规则,将模糊控制和PID控制相结合,构成SRM的模糊PID转速调节器,实现Kp、KI、KD 3个控制参数的自适应调节,从而获得在整个调速范围内不同负载下较好的调速特性。仿真试验表明,所提出方法避免了固定参数转速调节器的比例积分环节导致的低速、轻载工况下的转速超调与振荡,克服了单纯模糊控制所导致的调速误差。     

二维浅水狭航道船舶变速航行的有限元计算

本文从二维浅水波方程出发,采用有限元计算船舶变速驶进、驶出大坝升船机承船厢时的水动力学过程.二维浅水波方程理论把行驶船舶对水面的作用力直接加在二维浅水波方程里,以此来计算水表面波动和水平流速.水动力波产生的水动压力又影响到船舶的运动.本文研究船舶和水体的相互作用.它描述了水面波动、水平流速、船舶的纵倾角、船和厢底的最小间隙、以及承船厢受的水体总重量、水动力矩等重要物理量在船舶行驶过程中的变化规律.本文算例的结果和文献[5]给出的实验数据大体一致.计算结果还发现,船舶驶出承船厢时下沉和纵倾的幅度比船只驶进承船厢时要稍大一点.工程上应当予以重视.