共查询到20条相似文献，搜索用时 437 毫秒
1.
Using geotextile bag dehydrated soil to construct dikes for land reclamation to substitute conventional straw bags is an urgent need in Tianjin New Harbor, China. This paper introduces the method to build a dike for hydraulic filling. The soil for filling the geotextile bags was tested in wave trench ; the stress developed during construction was calculated by establishing a numerical model and compared with the tensile strength of the geotextile; the stability and settlement of the dike were estimated by performing centrifuge tests. Through this study, the following information was obtained: 1 ) The cohesionless silt with plasticity index less than 10 is suitable for filling the geotextile bags. The geotextile bag dehydrated soil consolidated very quickly even under the action of wave force. 2) A numerical model was devised to find the limit injection height and to calculate the tensile stress developed in the geotextile bags when they were piled up to form the dike. The calculated stress was compared with the strength of the geotextile, showing that the design is reasonably safe. 3) Centrifuge test results show that the designed dike will be stable and the settlement of dike will be less than the design requirement. 相似文献
2.
The mechanical characteristics of the weld joint were investigated by tensile test, microstructure test, and microhardness test. The welded tube NC bending tests were carried out to evaluate the weld on the formability of the QSTE340 welded tube. The results show that the wall thinning degree, cross-sectional deformation and springback angle increase significantly as the weld line is located on the outside of the bend compared with that located on the middle and inside, and the welded tubes produce nearly identical performance as the weld line is located on the middle and inside. The wall thickening degree decreases much as the weld line is located on the inside of the bend. So the welded tube can acquire good bending formability as the weld line is located in the region away from the outside of the bend. 相似文献
3.
采用离体花粉培养技术,研究了不同浓度的细胞外钙对百合花粉萌发和花粉管生长的影响.结果表明：在0.01％ Ca2＋度下花粉萌发和花粉管生长速率最快,高于或低于这个浓度,花粉管生长速率和萌发速率都显著被抑制.将快速生长的花粉管,转入Ca2＋浓度为03％的培养基中,花粉管的生长在几秒种内就被抑制.长时间0.3％ Ca浓度培养导致花粉管呈波浪形状.这种改变是不可逆的,当用pectinase处理或降低培养基中的钙浓度时,花粉管破裂.这些结果说明钙作为花粉管生长调节信号,对花粉管的生长具有直接作用和间接作用. 相似文献
4.
为研究一种新型强化传热管的传热效果,对光管、普通翅片管和螺旋槽式翅片管在不同流量条件下的传热特性进行了比较研究.实验中管程工质为水蒸气,壳程通入饱和液态水作为冷源.结果表明,螺旋槽式翅片管的换热量明显高于光管和普通翅片管,并且随着流体流量的增加,传热效率的提高也更加明显.当蒸汽温度140℃时,螺旋槽式翅片管沸腾传热系数... 相似文献
5.
朱康良 《兰州石化职业技术学院学报》2002,2(2):16-18
在深入分析对心型曲柄摇杆机构的几何特性和杆长关系的基础上 ,推导出许用传动角和最小传动角与摆角之间的不等关系式 ;提出了一种按最小传动角解析设计对心型曲柄摇杆机构的方法 ,能同时满足许用传动角要求与最小杆长和要求 相似文献
6.
齐俊高 《中学课程辅导(初二版)》2005,(12):39-39
December1st——BigTea Party(日)献茶节December10th——Nobel Day诺贝尔奖金授奖日December21st——Winter Solstice冬至日December24th——Christmas Eve圣诞节前夕December25th——Christmas圣诞节December30th——Kwanzaa宽扎文化节十二月份的节日$太原五中@齐俊高 相似文献
7.
8.
HUANG Wei-jun DENG Xian-he ZHOU Shui-hong 《重庆大学学报(英文版)》2006,5(1):8-12
1 Introduction A well known method to increase heat transfer from a surface is to roughen the surface by use of regular geometric roughness elements, such as transversely-ridged tube, spirally-ridged tube or converging-diverging tube, etc., on the surface… 相似文献
9.
With isopentane as working fluid, the heat transfer performances for corrugated, nodal and horizontal grain tubes are simulated. The structural parameters of the three kinds of tubes are compared with those of the plain tube. The numerical results using computational fluid dynamics are validated with theoretical values. For the corrugated, nodal and horizontal grain tubes, the heat transfer enhancements(HTEs) are 2.31—2.53, 1.18—1.86 and 1.02—1.31 times of those of the plain tube, respectively. However, the improved HTEs are at the expense of pressure losses. The drag coefficients are 6.10—7.09, 2.06—11.03 and 0.53—1.83 higher, respectively. From the viewpoint of comprehensive heat transfer factor, the corrugated tube is recommended for engineering applications, followed by the horizontal grain tube. 相似文献
10.
Rats were given alternating 1-min access to two tubes containing sucrose solutions that varied in concentraton (32% vs. 2%, 32% vs. 4%, 32% vs. 8%, and 32% vs. 16%). Lick rate for 32% sucrose was higher when the alternative tube contained a lower concentration solution than when both tubes contained 32% (a positive-contrast effect), and lick rate for the lower concentration solution (2%, 4%, 8%, or 16%) was lower when the alternative tube contained 32% than when both tubes contained the lower concentration solution (negative contrast effect). Proportion of licks made for 32% under contrast conditions tended to match the proportion of concentration available from that tube. Regression analysis of the ratio of licks made to the two tubes under contrast conditions as a function of ratio of concentrations available indicated a good fit to a power function with an exponent of 1.13, within the range of those typically found in human magnitude estimation studies of relative sweetness. 相似文献
11.
土工织物在岩土工程中的应用是近三十年来新兴起来的一门新技术.它已广泛应用于十多个基础产业部门兴建的工程中.但在房屋建筑中的应用例子尚属少见,本文作为一种尝试,将土工织物加筋薄层软土地基的成功经验加以介绍,并希望据此能进一步拓宽土工织物在工程中的应用领域. 相似文献
12.
亢延民 《淮南职业技术学院学报》2006,6(3):1-4
在冻结法凿井中,因局部冻结管断裂,造成盐水泄漏,会引起连锁断管反应,降低冻结壁强度,威胁冻结凿井安全,如何防止冻结管断裂或在局部断管后如何采取有效的补救措施避免事故的进一步扩大,是冻结法凿井施工中的技术难题;在冻结管断裂原因、防止冻结管断裂和处理冻结管断裂技术等方面进行了具体分析,供类似深井冻结法施工参考。 相似文献
13.
The filling construction of permeable geosynthetic tubes is considered. First, an analytical approach is developed to determine the internal pressure, tension and shape of the cross section of a geosynthetic tube based on its volume. An analytical solution for the drainage rate of the tube is then derived. The course of the filling construction is divided into several time intervals and the volume of the tube after each interval is obtained from the equilibrium of flow calculated from the drainage rate and filling rate. The validity of our analytical approach is tested by comparing our results with previously published experimental result. The results of this comparison indicate that our method is applicable for simulating the filling construction of permeable geosynthetic tubes. 相似文献
14.
This study addresses heat transfer performance of various configurations of coiled non-circular tubes, e.g., in-plane spiral ducts, helical spiral ducts, and conical spiral ducts. The laminar flow of a Newtonian fluid in helical coils made of square cross section tubes is simulated using the computational fluid dynamic approach. The effects of tube Reynolds number, fluid Prandtl number, coil diameter, etc., are quantified and discussed. Both constant wall temperature and constant heat flux conditions are simulated. The effect of in-plane coil versus a cylindrical design of constant coil, as well as a conical coil design is discussed. Results are compared with those for a straight square tube of the same length as that used to form the coils. Advantages and limitations of using coiled tubes are discussed in light of the numerical results. 相似文献
15.
赵鸣放 《河北能源职业技术学院学报》2007,7(1):65-66
本文简要叙述了煤矿许用刚性被筒炸药的正确组装方法,通过煤矿安全事故案例,论证了煤矿许用刚性被筒炸药的正确组装在煤矿安全生产中的重要性. 相似文献
16.
王月华 《泰州职业技术学院学报》2012,12(4):45-48
文章以60×40×4大体积混凝土采用整体一次性浇筑方案为基础,以一维差分法计算了混凝土的温度场,并用建筑工程中常用的拉应力计算公式计算了最大拉应力,结果显示一次整体浇筑方案有产生贯穿性裂缝的风险,没有达到安全系数k=1.15的要求,需要采取措施控制温升产生的拉应力。因此,在降低混凝土水泥用量的基础上,采用了外径为1.25cm钢管、水平间距为1.70m、铅直间距为1.60m（两层）的方案,通过循环水降低大体积混凝土凝结过程中水化热产生的温升,并提出温度应力监控措施,以便及时采取温控措施,实现信息化施工。 相似文献
17.
介绍了一种用于强化管壳式换热器壳侧传热和支撑管束的螺旋折流片新型结构,该结构是对换热器管子相间地套上螺旋折流片以产生旋涡流动.研究模型是在正方形布置的4个管子中的2个对角管子套上螺旋折流片后形成的通道,利用FLUENT软件对该上述四管通道模型的流场和温度分布情况进行了数值模拟;分析了四管通道模型中螺旋折流片对强化传热和流动阻力随雷诺数的变化关系的影响.算例结果显示该新型结构可比相同尺寸的光管通道中的情形传热系数提高约40%～55%,同时也将伴随较高的流动阻力.可以相信螺旋折流片式换热器将会在许多工业领域有良好的应用前景. 相似文献
18.
余泽红 《湖南广播电视大学学报》2004,(4):95-96
王村公路大桥是一座中承式特大桥，此类大桥施工的关键在于钢管拱肋的制作安装、管内混凝土浇注和钢管的防腐处理。施工质量的好坏直接影响到桥梁的使用安全和使用寿命。 相似文献
19.
明清时期,随着堤防的增加,堤防的重要性明显提高,有关修防的规章制度逐渐建立起来。拟就明清时期堤防管理制度中修防制度、修防经费的来源以及官督民修与绅衿作用等问题作进一步的探析。 相似文献
20.
Charlie Swan 《Support for Learning》2021,36(4):555-571
This article explores how gastrostomy feeding tubes can impact the early childhood education and care (ECEC) experiences of children. It presents findings from a small-scale study, which utilised the perspectives of early years educators and parents. The findings indicate that feeding tubes have both an opportunistic and restrictive impact within ECEC. Opportunity was evident through improved nutrition and health, which allowed familial respite and an increased attendance of ECEC. This enabled opportunities for social and explorative interactions. However, the complexities of having and supporting a feeding tube made accessing types of play and exploration challenging. Collaboration between the educators and parents was a crucial tool for success. Educators felt with experience and teamwork they could ensure the needs of children were met innovatively and safely. However, it was concluded clearer advice for attending ECEC settings with a feeding tube would benefit all involved and instil a sense of readiness. 相似文献