新型无轴承无刷直流电动机结构与模型研究

目前研究的无轴承电机均是将电机和转子悬浮磁路合为一体,两个磁场的叠加一方面容易造成磁饱和,使电机的承载能力下降,影响电机的稳定悬浮;另一方面电磁转矩与径向悬浮力之间具有很强的非线性耦合,而实现解耦控制是非常复杂的.将无刷直流电机的优点与磁悬浮轴承的优点结合,提出一种六自由度可控的无轴承无刷直流电动机结构,通过研究其悬浮原理和运行原理,建立了转子偏心时的精确数学模型和PWM(脉宽调制)调速的精确数学模型,经仿真测试,表明了这种电机结构的合理性.主要特点是承载能力高且电磁转矩控制与径向悬浮力的控制相互独立,无需复杂的非线性解耦控制.     

刷镀快速镍修复发动机曲轴的研究

利用ＭＭ２００型磨损试验机研究了快速镍刷镀层的耐磨性,通过单因素试验和正交试验,揭示了工作电压和电极相对速度对镀层耐磨性影响的规律,得到最佳工艺规范参数。制定了曲轴的刷镀工艺,并应用它对Ｌ１９５柴油机的曲轴进行了刷镀修复,然后装机在水力测功机上进行各种工况的耐久性试验。结果表明：刷镀快速镍修复的曲轴,耐磨性和结合强度高,能够承受高速重负荷,刷镀修复曲轴技术上可行,经济上合算,为刷镀快速镍修复发动机曲轴提供了依据。     

Disease eradication and propagation of the initial seed potato material in Estonia

Summary The EVIKA Research Centre has developed a disease eradication system for the initial material of seed potato, which consists of 1. Selection of the initial material for eradication, plant thermotherapy, meristem tip cultivation and testing for viruses; 2. Re-eradication (thermotherapy of test-tube plants, cultivation of meristem tips, testing for viruses, testing of varietal quality and yield of disease-free meristem clones, and the selection of meristem clones with best varietal characteristics; 3. Renewing of the initial material (all processes as above, but the initial material is selected from the seed potatoes grown for at least 3 years in the field). Field trials were conducted after the second cycle of eradiaction to determine whether the plantlets were true-to-type and to assess the yield, disease resistance and tuber dry matter. Recently we have also started in vitro testing of meristem plants resistance to late blight, hoping that this approach will improve the selection efficiency. Propagation and growing of the seed tubers consists of 3 main steps: 1. Plantlet propagation in vitro; 2. Greenhouse propagation in plastic rolls; and 3. Planting the first generation tubers in the field. Under our conditions it is the cheapest, simplest and most effective way. Multiplication of the meristem-derived plants is done by shoot tip cuttings in a greenhouse in plastic rolls with peat as the growing medium. The first generation of seed tubers is grown in the field. In our trials plant productivity was affected by the method of multiplication, growing conditions and genotype. The highest yield per hectare was obtained with plants multiplied in plastic rolls. The in vitro plants had more tubers per plant than plants multiplied in plastic rolls. In seed production fields the productivity of plants was more influenced by following our instructions than by multiplication and growing methods. The number of tubers per plant obtained with over 0.5 million plants was 6.5–9.0. In the second generation of seed tubers, grown under equal density, the greater-sized tubers gave more tubers with lower weight than the smaller-sized tubers. Cutting tubers had no effect on the plant development and tuberization.     

冷轧带肋钢筋工程的应用分析

结合冷轧带肋钢筋和热轧钢筋在工程中的应用,主要对冷轧带肋钢筋构件进行基本性能分析和经济效益的分析比较,并阐述了冷轧带肋钢筋的诸多优点,以及加大推广应用冷轧带肋钢筋的建议。     

对辊柱塞式成型机设计与试验

基于生物质固化成型领域活塞冲压式成型机能耗低、生产率低和模辊式成型机生产率高、能耗高的特点,提出一种新型对辊式成型方式,并设计和制造了样机。该成型机压辊圆周上均布了一系列柱塞,运行过程中压辊柱塞与环模模孔相互啮合,避免了成型孔之外的物料受到压辊的挤压与摩擦。为测试该成型机的性能,进行了正交试验研究,结果表明,该成型机的较优成型参数为:含水率15%,成型模具长径比5.25,主轴转速47.25 r/min。以木屑为原料,在较优成型参数的条件下进行了成型机性能指标的测试,结果表明,该成型机生产的成型颗粒直径为10 mm,成型颗粒密度为1.15 g/cm3,机械耐久性为96.28%,生产率为75 kg/h,能耗为56 k W·h/t,成型率为95%,工作噪声为79 d B,各项指标均达到设计要求,实现了连续稳定生产。     

Intestinal microbiota differentially affect brush border enzyme activity and gene expression in the neonatal gnotobiotic pig

To study microbial influence on intestinal development pertaining to nutrient digestion, two separate gnotobiotic experiments were performed, each with 16 piglets allocated to four treatment groups: germfree (GF), monoassociation with Escherichia coli, monoassociation with Lactobacillus fermentum or conventionalization with faecal bacteria (CV). Enzyme activity and gene expression of lactase phlorizin hydrolase (LPH) and aminopeptidase N (APN) were measured in isolated enterocytes, harvested on day 14, using specific substrates and quantitative PCR respectively. Enterocytes of CV pigs had reduced APN activity, but had increased gene expression relative to GF, making the specific activity:mRNA (A:G) ratio dramatically lower (p < 0.05). Similarly, LPH A:G ratio was significantly reduced (p < 0.05) in enterocytes of CV pigs as compared with GF. The results of co‐incubation of L. fermentum, E. coli and faecal bacteria with APN indicate a direct relationship between enzyme inactivation and specific A:G ratio in enterocytes. We conclude that enterocyte up‐regulation of APN expression occurs as either a direct response to microbial colonization or as a feedback mechanism in response to reduced enzyme activity through microbial degradation. This mechanism may play a role in ensuring effective competition of the host with the intestinal microbiota for available nutrients.     

变间距梳刷式枸杞采收装置优化设计与试验

为实现枸杞机械化采收,提高枸杞采摘的采净率、降低损伤率,提出一种在沟槽凸轮的引导下,压板迫使骨架侧向张开,进而调节梳刷指间距的设计方案。通过对枸杞自然特征和物理参数测量分析,建立了梳刷指变间距控制部件的数学模型,并利用Matlab对其关键零件进行结构设计优化。以宁杞1号为研究对象,设计多参数变量的正交试验,以采净率和损伤率作为评价指标,得到对采摘效果影响程度由大到小的梳刷指参数依次为弹簧钢长度、指间距、弹簧钢直径;最佳的梳刷指参数组合为:指间距为8 mm、弹簧钢长度为45 mm、弹簧钢直径为1.1 mm。在宁夏农科院枸杞研究所进行实地采收试验,结果表明:采净率为90%,损伤率为8.41%,满足枸杞采收的工作要求。     

基于Padé模型降阶法的车辆侧倾动力学研究

为简化对车辆侧倾动力学的研究特别是对车身侧倾角的估算和控制,提出针对车身侧倾角的Padé模型降阶方法.该文首先建立了线性三自由度车辆模型,并在此基础上推导出了车身侧倾角的传递函数,由于此传递函数的高阶特性难以用于车辆侧倾动力学的计算与控制中,所以接着对所推导出的侧倾角传递函数进行降阶处理.又考虑到车身侧倾的低频特性以及Padé模型降阶法在低频区能有较好的拟合效果,该文采用Padé模型降阶法对车身侧倾角传递函数进行降阶处理.为了验证降阶后模型的有效性,从时域、频域和复域3个方面分别进行了论证,并通过Truck Sim和Matlab进行了仿真对比.结果表明降阶后的模型在低频区具有较好的逼近效果,此降阶方法可以简化对车辆侧倾动力学的研究,并可以将此降阶模型应用于车身侧倾角的估算和控制中.     

新型生态草皮卷生产专用基质研究

[目的]探讨适合不同类型草皮卷生产的专用基质。[方法]研究不同的基质体积配比对多年生黑麦草、改良型狗牙根、高羊茅+多年生黑麦草组合地上部分分蘖数、地下部分根长和根数、根冠比、成毯性等的影响。[结果]狗牙根草皮生产基质以废菌棒∶园土∶堆肥土=3∶4∶3为宜,多年生黑麦草以炭化谷糠∶园土∶泥碳=3∶4∶3最好,高羊茅+多年生黑麦草以秸秆∶园土∶堆肥土∶煤渣=2∶3∶3∶2为宜,可作为新型生态草皮卷生产的专用基质。[结论]试验结果为生态草皮卷规模化生产提供了理论依据。     

棉秆切碎器的浮动夹持喂入机构设计

针对棉秆切碎收获机械介绍了一种新型带自调节、夹紧和主动输入功能的喂入机构。同时,对其结构组成、工作原理和关键部件参数设计分别进行了详述,并验算了最大通过量,分析了几种改变切碎长度的方法。实践表明,该机构还可适用于其它硬质冠状秸秆切碎前的强制喂入,具有结构简单、稳定性好、使用维修方便以及使用寿命长等特点。