刚性芯桩组合桩复合地基动力试验研究

基于桩型优化的思想,设计了水泥土桩和CFG桩组合桩复合地基。通过大比例现场模型试验,研究在爆破地震动作用下刚性芯桩组合桩复合地基的动力特性和动力响应的规律及其影响因素。得到荷载与主频及加速度之间的相关规律。     

CFG桩复合地基有限元分析

本文针对银川地区开始使用CFG桩处理的地基,结合实际工程案例,分析不同荷载作用下复合地基的沉降情况;对CFG桩复合地基进行了有限元模拟,考虑桩长、褥垫层厚度的影响,计算分析不同荷载作用下的沉降情况。为银川地区后续工程提供经验和借鉴。     

人工践踏对无土草坪基质的影响

本试验采用人工践踏的方式,研究了不同组合配比的基质对无土草坪耐践踏性的影响。结果表明,良好的无土草坪基质配比及适合的厚度是保证无土草坪优良的耐践踏性及观赏性的关键。本试验中,草坪草生长基质层和弹性材料层均为25 mm,结构合理、厚度适中,克服了现有草坪基质薄、持水力差的缺点。在相同践踏强度下,能维持较高水平的草层高度、草坪盖度和草坪草分蘖数,分别达到了5.14 cm、97.60%和123.97 个·dm-2,且停止践踏后草坪质量能快速恢复。均匀混合的草坪草生长基质层和弹性材料层,在厚度一致的前提下并不耐践踏,实际效果不好。土壤坪床的处理效果最差。因此,具有独立的草坪草生长基质层和弹性材料层且厚度适中的基质,适用于生产耐践踏性好的无土草坪。     

利用非均质模型优化组合段塞方式室内试验研究

由于长期注水开发的区块普遍存在着储层物性差别大、层内及层间非均质性对注水开发效果的影响非常突出的特点,因此采用非均质岩芯模型进行室内驱油试验具有极其重要的意义。本试验利用非均质岩芯模型,对段塞组合方式进行优化,研究复合驱配方体系对驱油效率的影响。以此制定科学合理的配方体系,充分发挥化学驱的作用来提高开发效果,实现增储稳产目标。研究内容:(1)采用长岩心非均质模型进行实验,研究并取得储层平面非均质性对驱油效率影响的规律性认识;(2)采用不同段塞组合方式,研究段塞组合对驱油效率影响的规律性认识。从而指导注入方案的开发调整和剩余油的挖潜。     

隧道地震动力响应影响因素研究及分析

在人类人口急剧增加和世界经济不断发展的今天,地上建筑受到空间发展的影响约束,已经不能满足人类对于可持续发展和生活舒适性的要求,所以地下建筑的发展就显得尤为迫切和重要,而地下结构的建设不可避免的要遭遇到断层和高烈度地震区,因此研究地下结构物在地震荷载下的动力响应就显得尤为重要。隧道的震害形式多种多样,而且影响地震动力响应的因素也非常多,隧道地震动力响应影响因素主要包括了隧道的埋深,周围岩体的地质地形,隧道结构的形式,支护结构,施工方法,本文主要从前三个方面进行阐释。     

樊庄区块煤储层非均质性的构造控制作用

樊庄区块煤储层发育的非均质性较强,直接导致了煤层气井间产能差异较大。在对樊庄区块进行构造精细解释和地应力分析的基础上,结合该区块煤储层的煤体结构和裂隙发育特征,深入研究了构造变形和现代构造应力场对煤储层非均质性的影响。研究表明,樊庄区块褶皱构造比较发育,主要为轴向近NS的宽缓褶皱,褶皱轴部构造裂隙发育,对煤储层有利;该区煤层中断裂构造非常发育,以正断层为主,越靠近断层,煤层变形破碎越明显,裂隙越发育,但在寺头断层附近为强烈变形的软煤发育带,对煤储层不利。现代构造应力场对煤储层的影响主要表现为对裂隙"开、闭"的控制,水平主应力差越大,越利于煤储层裂隙的开启。     

预应力混凝土T梁产生裂缝的原因及预防分析

<正>1混凝土裂缝产生的原因分析裂缝对混凝土外观质量来说是一种缺陷,有些裂缝影响外观质量,有些裂缝则直接影响构件的安全使用。混凝土出现裂缝是一个很普遍的现象,一般将其分为两类,一类是在外荷载作用下产生的裂缝,即结构性裂缝。另一类裂缝是由变形引起的,也称非结构性裂缝,产生这类裂缝的原因是由于混凝土变形得不到满足,在构件内部产生自应力,当该自应力超过混凝土允许拉应力时,导致混凝土开裂。预应力混凝土T梁产生非结构性裂缝的原因很多,如温度和湿度的变化、混凝土的脆性和不均匀性、原材料不合格、模板变形、基座不均匀沉降、施     

预应力作用下桥式起重机变截面主梁振动分析

本文利用传递矩阵方法分析预应力作用下桥式起重机变截面主梁的振动特性并推导出频率方程;结合算例讨论了预应力对桥式起重机变截面主梁固有频率的影响;利用振型叠加法得出冲击荷载作用下预应力梁的瞬态响应,分析了预应力以及冲击荷载的作用时间步长对瞬态响应的影响。计算结果表明,预应力作用下桥式起重机变截面主梁的振动频率随着预应力的增大而逐渐增大,而且几乎具有线性关系,这为工程设计人员提供相应的参考。     

PEG胁迫对2种冰草叶片显微和超微结构的影响

为了研究PEG渗透胁迫对冰草叶片细胞结构的影响,试验以两种抗旱性不同的冰草叶片为材料,采用石蜡切片法和电镜样品制片方法,进行叶片显微和超微结构特征的观察和比较研究,以进一步探讨干旱对冰草的显微结构和超微结构的影响。结果表明:PEG胁迫对2种冰草叶片厚度、上表皮厚度和下表皮厚度、主叶脉直径、主脉导管直径和肋状突起高度产生不同的影响;叶片细胞出现严重的变形,对叶绿体超微结构产生严重的影响,造成叶绿体被膜褶皱,基粒片层扭曲变形,叶绿体基质中的淀粉粒和质体小球明显减少。     

弹性飞行器飞行仿真研究

现代飞行器的设计日益追求高速度、超机动性和敏捷性,使得现代飞行器越来越呈现出高速度、轻结构、大柔性和低阻尼的特点。对于导弹或者火箭来说,它们的射程和载重量任务要求它们具有大质量,且长细比越来越大,因此弹性低阶频率也越来越低,弹性变形和弹性振动对导弹弹道仿真的影响不能再忽略。本文发展了一种将飞行力学与气动弹性力学相结合的飞行仿真工具,建立了刚性导弹和弹性导弹的全弹道打靶仿真模型,在Matlab/Simulink平台下搭建各模块,用于研究弹性导弹全弹道仿真过程中的运动参数响应。     

黄土母质生土上4种豆科牧草根系生长特征的研究

以黄土母质生土为供试土壤,采用根管土柱栽培方法,研究了苜蓿(Medicago sativa L.)、草木樨(Melilotus officinalis Desr.)、小冠花(Coronilla buxifolia Hance.)和红三叶(Trifolium pratense L.)4种豆科牧草根系生长规律的差异。结果表明:4种豆科牧草根系各项指标的增长随生育期变化(时间构型)皆呈"S"型增长模型,可划分为缓增期、速增期和顶峰期,在一个生长季内,根系不存在衰老死亡生物量急剧减少的现象;4种豆科牧草根系垂直分布存在很大差异,根系生物量空间呈"T"型分布,其垂直递减率符合指数递减方程Y=A·e^-bx;4种豆科牧草根冠生长模式分属于4类:根苗增长同步型(小冠花)、苗强持久增长型(草木樨)、根强持久增长型(苜蓿)和苗弱根弱增长型(红三叶草),豆科牧草根系峰值常出现在生育后期晚于冠层。本研究结果对建立黄土母质生土上牧草高产栽培技术体系以及促进根苗系统的协调生长提供了依据。     

内蒙古典型草原羊草生长季内的地上生物量动态对降水的时滞响应

在草地生态系统与气候变化关系的研究中,植物生长动态对气象因子的响应是该领域的研究热点之一。本文以内蒙古典型草原生态系统的降水和生长季内羊草（Leymus chinensis）地上生物量的动态变化数据为研究对象,采用灰色时滞关联分析模型探索降水对羊草地上生物量动态的最佳时滞效应量,并采用灰色时滞GM（1,2,τ）模型证实降水对羊草地上生物量时滞效应量的合理性。结果表明：降水对羊草生长的最佳时滞效应量随年份而变,以2015-2016年的数据为例,最佳时滞效应量分别是τ=4天和7天,且降水对羊草生长动态的影响表现出明显的累积效应和时滞效应。本研究结果将有助于探明降水对羊草地上生物量动态变化的影响机制,并为天然草地植物动态定量建模与预测提供数据依据。     

Does the A-line ARX-lndex provide a reasonable assessment of anaesthetic depth in dogs undergoing routine surgery?

The monitoring of anaesthetic depth is usually based on the subjective assessment of the patient. An objective assessment of anaesthesia has only recently become possible. The auditory-evoked response has predictable changes in response to increasing doses of anaesthetic agents. Recent advances have brought about a regression model with exogenous input of the auditory-evoked response, the A-line ARX-Index (AAI Index). The AAI Index is a dimensionless number between 0 and 100. This technology has been incorporated into the AEP (auditory-evoked potential) monitor that is utilised to assess anaesthetic depth in humans. This study was undertaken to determine if the AEP monitor was useful in dogs. Ten dogs were enrolled in the study. After a full clinical and otoscopic examination, dogs were premedicated with acetylpromazine and morphine. Anaesthesia was induced with thiopentone and maintained with halothane. End-tidal carbon dioxide, temperature, pulse oximetry, blood pressure and the electrocardiogram were monitored and recorded every 5 minutes. Anaesthetic depth was assessed as either being adequate or inadequate by the anaesthetist during surgery. An AEP monitor was attached to the patient and automatically collected AAI Index data. The anaesthetist was blinded to the AEP monitor. Following the completion of the surgical procedure, the patient was allowed to wake up with the AEP monitor attached. The AAI Index was analysed to compare adequate with inadequate anaesthesia during the period of surgery and awake with sleep data during recovery. All AAI Index values associated with inadequate anaesthesia were greater than 31 while adequate values were less than 35. The difference between the groups was statistically significant and the power was 0.97. Statistically, the awake and sleep values were significantly different with a power of 0.99. From this study it can be concluded that the AAI Index shows good prospect for the evaluation of anaesthetic depth in dogs undergoing surgery. A larger study is needed to confirm these results.     

Impact of conformation traits on functional longevity of Holstein cattle of Iran assessed by a Weibull proportional hazards model

A Weibull proportional hazards model was applied to evaluate the effects of 18 linear type traits on the functional length of productive life in Holstein cattle of Iran. Culling data and classification scores on 44,179 cows with first calving from 1996 to 2004 were used. The data included up to 55% of censored records. Length of productive life was defined as the number of days from first calving until last test day or censoring. The significance of each type trait was tested by a likelihood ratio test comparing the full model (with one particular type trait) with reduced models (without any of the type traits). Analyses were performed for each type trait one at a time which included as a covariate in the model. The strongest relationship between length of productive life and type traits were found for fore udder attachment, udder depth, udder cleft angularity and loin strength. Body traits except angularity had minimal effect on functional longevity. Some traits such as udder depth, rear legs side view and foot angle showed an intermediate optimum with respect to longevity and extreme scores of these traits increased risk of involuntary culling. Results of the present study showed that improvement of conformation traits, which is more associated with functional longevity, is a useful way to increase functional length of productive life.     

Modelling the static and dynamic responses of total heat production of broiler chickens to step changes in air temperature and light intensity

1. The objective of this work was to explore the possibilities of modelling the static and dynamic responses of total heat production of broiler chickens to step changes in temperature and light intensity (light-dark alterations) using compact dynamic model structures. 2. Seventy-seven experiments were performed in an open-circuit respiration chamber to measure the dynamic response of heat production to step variations in temperature and light (on/off). The animal responses were modelled using transfer function model structures. 3. It was demonstrated that the complex process of the dynamic response of heat production of broiler chickens to step changes in air temperature and light-dark alterations can be modelled assuming 1st order dynamics. The coefficient of determination between measured and simulated heat production was on average 0.83 for responses to air temperature and 0.93 for responses to light-dark alterations.     

Band placement of lime and superphosphate for ladino clover in an acid oxysol

In a pot experiment with the A₁ (topsoil) and B₂ (subsoil) horizons of a Clovelly soil, it was found that although increasing the rate of band‐placed lime from 265 to 2650 kg per ha did not significantly influence the yield of Ladino clover, considerably higher yields were obtained where the pH of the entire soil mass was raised from approximately pH 5.0 to 6.0 by liming.

It is suggested that Al‐toxicity is a major limiting factor in this soil and may largely account for the response to liming. Increasing the band‐placed superphosphate application from 265 to 2650 kg per ha resulted in highly significant yield increases. Considerable root development occurred in the superphosphate bands as compared with limited root development in the lime bands. Significantly higher yields were obtained from the A₁ horizon than from the B₂ horizon. Differences due to depth of placement of the lime and superphosphate, placement of the lime and superphosphate in a single band as opposed to separate parallel bands, and the use of powdered and granular superphosphate were recorded in the first cut but not in the second.     

不同树龄小叶锦鸡儿干旱降水过渡时期用水策略研究

在阿古拉生态水文试验区的固定沙丘上选取了两组具有代表性的3、5和9年生小叶锦鸡儿灌丛,采用氧稳定同位素技术,在连续15 d内比较了干旱、两次降水后(15.6、33.1 mm)灌丛内距离基茎3等分点及边缘处土壤水、降水与植株木质部水的δ¹⁸O值,研究了小叶锦鸡儿从干旱到雨后的用水模式变化,同时结合不同位置根系密度和灌丛内不同位置水分动态分析其变化原因。结果表明:小叶锦鸡儿在干旱条件下主要靠减少体内水量损失来维持生存而非利用深层土壤水,可能会将表层凝结水作为用水来源;雨后1 d内3种小叶锦鸡儿植物水δ¹⁸O值均趋向降水,3 d内3、5年生小叶锦鸡儿植物水δ¹⁸O值变化显著,9年生则基本不变;雨后5 d内10~60 cm为3种树龄小叶锦鸡儿的主要吸水层位,0~10 cm土壤水不是稳定的用水来源,3、5年生小叶锦鸡儿灌丛1/3处和边缘处及9年生边缘处水会优先被利用;随树龄增加小叶锦鸡儿的浅根系密度显著增大使其能有效利用降水,但灌丛下深层土壤水补给愈发困难,不利于地区水文平衡。建议人为控制大树龄小叶锦鸡儿的分布密度。     

Protein and fat utilization in lactating sows: II. Challenging behavior of a model of metabolism

The objective was to challenge the behavior of an existing mechanistic model of sow metabolism using data from a study that determined effects of fat and amino acid intakes on milk production, body and mammary composition in sows nursing 10 to 12 pigs. Sows were second through fourth parity; litter size was standardized at 12 pigs within 3 d of farrowing, and lactation was for 20 d. Diets were formulated and fed to provide three different amounts of protein intake and two different amounts of fat intake. Data were used to challenge the behavior of an existing mechanistic, deterministic, dynamic model for describing variation in milk production and changes in body composition. Nutrient intake and initial body weights and compositions were used as direct inputs into the model. The model could describe milk production within 1 SD of the mean on all rations. The model described body fat within 1 SD of observed values, but overestimated final body protein by approximately 30% (or between 1 and 2 SD). The model described the change in body fat and protein in response to 5% additional fat in the ration within 1 SD of observed (simulated - observed = -1.1 kg for protein and -0.7 for fat). The simulated response to dietary protein was within 1 SD (2.6 kg): simulated response from medium to high protein was 1.0 kg, observed 1.2; simulated response from medium to low was -0.7 kg, observed 0.3 kg. Thus, the model was not as accurate in describing the body protein response to a low-protein diet and overall, overestimated the retention of body protein. This model has utility for setting specific research hypotheses and may be amenable to use by nutritionists in a variety of applications. Further improvement in the ability of the model to describe metabolism and production of lactating sows is limited by a severe lack of data on metabolic interactions. Data on rates of muscle protein synthesis and proteolysis and interactions between amino acids, fatty acids, and glucose are needed to improve this and other models of sow production.     

草食动物与草地植物多样性的互作关系研究进展

动物-植物互作关系一直是草地生态学研究的核心问题之一。在草地放牧系统中的动植物界面上,生物多样性的作用突出而敏感,因此,对动物与植物多样性的互作关系探讨,有益于深刻阐释放牧系统的稳定性与持久性机制。本文综述了有关草食动物对草地植物多样性的作用结果、影响因素、作用机制,以及植物多样性对草食动物生产性能、多度和多样性影响的研究现状,并就今后的研究方向提出几点建议:扩展动物多样性及不同动物组合对植物多样性的作用机制研究;加强有关植物多样性变化对草食动物、特别是大型草食性动物的反馈作用过程研究;加强对动物采食行为的深入理解,尤其是动物采食对植物多样性响应机制的认识;加强草食动物与植物多样性之间的动态互作关系研究,以及这种互作关系变化对草地生态系统过程及功能的影响研究。     

The influence of a water-in-oil emulsion on humoral immunity

A strategy for research of immunostimulants is best served choosing a way by which the immune response can be studied without being complicated by a combination of effects originating both in adjuvant and antigen. This means that adjuvant and antigen preferably are applied with an interval and by different routes. In our model an adjuvant (a W/O emulsion) was applied intraperitoneally, whereas the antigen was injected intravenously. The stimulatory effect on the splenic plaque forming B-cell response depended on the dose of antigen, on the interval between adjuvant and antigen application, on the mouse strain used, and on the quality of the antigen with respect to the intrinsic adjuvanticity of the antigens.