钢支撑代替混凝土支撑可行性分析

在地铁深基坑施工中，围护结构对基坑的安全起着至关重要的作用。本文依据合肥地铁一号线明光路站，施工过程中，由于车站3号出入口为出土口，原计划的第一道钢筋混凝土支撑无法实现，更改为钢支撑，通过有限元分析软件MIDAS-GTS\NX，建立二维模型进行数值模拟，对围护结构的变形和地表沉降进行分析，结果表明：第一道支撑采用钢支撑代替钢筋混凝土支撑对围护结构的侧移值影响不大，钢筋混凝土支撑控制地表沉降的效果要比钢支撑好，对今后类似工程变更提供依据。     

透光抚育对“栽针保阔”红松林中红松生长过程的影响

[目的]通过研究长白山地区不同透光抚育强度下"栽针保阔"阔叶红松林中红松的生长情况,揭示透光抚育对"栽针保阔"红松林中红松生长过程的影响规律,旨在为阔叶红松林的恢复、经营提供有力的科学依据。[方法]研究5种透光抚育(未采伐对照、低度择伐、中度择伐、强度择伐及上层皆伐)对红松生长的影响。[结果]红松在群落中的地位随着透光抚育强度的增大逐步得到提升,同时透光抚育能够显著提高"栽针保阔"红松林内红松优势木(63.4%~146.5%、64.6%~158.6%)、平均木(57.9%~271.1%、42.5%~261.7%)和被压木(56.5%~182.6%、95.5%~245.5%)的树高和胸径,且呈现出随透光抚育强度的增大而递增的规律性。[结论]透光抚育能显著提高红松树高和胸径生长。     

遮荫对10种地被植物光合特性的影响

为了探讨地被植物在不同遮荫条件下的适应性,本研究以10种地被植物为材料,对其在不同光照条件下的生长状态、日平均净光合速率、表观量子效率及光补偿点进行分析.结果表明:遮荫水平对10种植物的光合有很大影响,10种植物能忍受的遮荫程度不同.对旋覆花、甘野菊、大叶铁线莲、青杞、委陵菜来说,全光比较合适；对蛇莓、匍枝毛茛、匍枝委...     

Papillary muscle measurements in cats with normal echocardiograms and cats with concentric left ventricular hypertrophy

BACKGROUND: Papillary muscle hypertrophy can occur in conjunction with, or as the only indication of, hypertrophic cardiomyopathy or other diseases that result in left ventricular concentric hypertrophy (LVCH). Assessment of papillary muscle size is usually subjective because objective measures have not been reported. HYPOTHESIS: The study hypothesis was that papillary muscle dimensions are different between normal cats and cats with LVCH. ANIMALS: Echocardiograms from 44 normal cats and 40 cats with LVCH were included in the study. METHODS: All measurements were taken from the right parasternal short-axis view at the level of the papillary muscles at end-diastole. Three methods were used to assess papillary muscle size: the area subtraction method, the direct area trace method, and the diameter method. Measurements were compared between cat groups and method comparisons were made among methods for area determination. RESULTS: Cats with LVCH were older and had significantly greater left ventricular septal and free wall thicknesses and larger left atrial measurements than normal cats (P < .0006). Papillary muscle measurements were significantly greater by all measurement methods in cats with LVCH than in cats with normal echocardiograms (P < .0001). The area subtraction method and direct area trace method showed moderate agreement. CONCLUSIONS AND CLINICAL IMPORTANCE: Papillary muscle measurements were larger for LVCH cats than normal cats; however, some overlap was present. The establishment of these objective measures adds to the echocardiographic examination of cats.     

步行轮式气垫车围裙—地面阻力特性分析

对步行轮式气垫车围裙－地面阻力特性进行了分析。建立了步行轮式气垫车围裙－地面阻力的精确数学模型，并进行了试验验证。探讨了几个主要因素对围裙－地面阻力的影响。     

地源热泵技术在中国温室设施中的应用探讨

当前在中国温室设施中应用和推广地源热泵技术尚存在诸多不利因素,大大限制了该项技术在设施农业领域中的发展。为探寻合理的解决途径,对地源热泵空调系统的关键技术和其在中国的发展概况进行了相关的阐述和分析,并以中国农业大学上庄实验站已经建成使用的地下水式温室地源热泵空调系统为实例,介绍该系统的组成、工作流程、性能参数和使用情况,探讨温室地源热泵空调系统在推广和使用中可能出现的投资较高,长时间运行性能不稳定等问题,分析其原因并提出相应的对策建议。     

Einfluss von grundwasser und trittbelastung auf den prozess der torfmineralisation und die stoffbilanzen: Influence of ground water and footprints on process of peat mineralization and nutrient balances

Pasture with burdening on peat-bog done four times a year has more positive effects on the water balance than twice grassland use. The saving of water that has been determined by lysimeters evokes no positive effects on the N-, P-, K- or Ca-balance. Due to the lower depth of the plant roots under lowland bog used for pasture more nutrients were leached into the ground water. The soil compression leads to anaerobic conditions. Therefore the phosphorus becomes more mobile and migrates into the outlet. The effect on the peat mineralization and the nutrient balances was not as clear as assumes, because other parameters like the combination of the vegetation formation and the age of the plants also had a strong influence on the factor. The younger plants from the pastures have show higher nutrient contents so that the nutrient export is higher and the balance becomes more negative.     

杉木人工林直径分布BP模型的研究

以相对直径作为输入向量,以株数累积频率作为输出向量,建立直径分布的BP神经网络模型;用杉木人工林直径分布的实际数据训练,选出的最佳模型,拟合精度为99.03%,检验精度为97.64%,所选模型没有系统偏差.与Weibull分布模型相比,具有较好的拟合效果.研究结果进一步表明,人工神经网络是一种有效的林分直径分布模拟技术.     

地面覆盖对花椒园热量平衡的影响

对花椒林地进行覆膜、覆秸秆和种植三叶草3种方式覆盖,测定不同覆盖条件下冠层的辐射能环境、热量平衡及水分环境.结果表明,地面覆膜、覆秸秆和种植三叶草条件下,地面反射率提高,增加了冠层净辐射,树冠下层接受的反射辐射分别较对照提高69.1%、48.0%和35.7%;树冠中部净辐射能分别较对照提高53.3%、26.3%和0.8%.在热量平衡中,覆膜、覆秸秆和种植三叶草的花椒林潜热通量分别占净辐射能的60.2%、62.4%和65.8%,感热通量分别占净辐射能的36.5%、34.0%和30.6%,土壤热通量分别占3.3%、3.6%和4.2%.     

耐荫、半耐荫地被植物在广州公园中的应用

耐荫、半耐荫地被植物是营建复层植物景观的重要元素。在对广州公园进行调查研究基础上,文章归纳总结了耐荫、半耐荫地被植物的种类,并根据园林用途对其进行归类。共有34种,隶属25科33属。经分析,这些植物与其他园林要素之间常见的配置方式有路缘配置、与山石相配置等7种。