间苯二酚-苯酚-甲醛树脂胶的快速老化性能试验

通过10、15、30和50次煮佛-干燥循坏人工快速老化处埋对间笨二酚-苯酚-甲醛(RPE)、酚醛(PF)树脂胶胶合试件以及实木(solid wood)试件的木块顺纹剪切强度进行比较。试验结果表明:RPF胶的耐候性优于PF胶的耐候性,研制的RPF胶是一种性能优良的耐候性结构用胶。     

论直剪试验的常见问题与对策

本文论述了直剪试验的方法及在直剪试验中常见问题，并提出相应的解决方法。     

pinⅡ基因在转基因大白菜DH纯系和试配F1代的遗传及表达

马铃薯蛋白酶抑制剂基因-Ⅱ(pinⅡ)是一类控制丝氨酸蛋白酶抑制剂PI-Ⅱ合成的抗虫基因.为了比较pinⅡ基因在转基因大白菜纯系和杂种中的表达特性,为抗虫新品种选育提供理论指导,本实验以转基因大白菜双单倍体纯系(DH系)的5个自交系和与常规育种亲本材料试配的3个F1杂交组合为试材,利用标记性状(除草剂抗性)对试材进行转...     

高压静电解冻技术对牛肉品质的影响研究

[目的]为了探讨高压静电解冻牛肉对其品质的影响,从而对此技术的推广应用提供理论依据。[方法]采用带有高压静电技术（HVEF）装置的冰箱和普通冰箱解冻同一头牛的外脊部位肉样,通过比较解冻时间和肉质分析结果。[结果]表明,带有高压静电装置的冰箱解冻牛肉比较普通冰箱解冻牛肉时间缩短16.67%,解冻失水率减少7.0%;高压静...     

高层建筑结构体系简析

随着各种新技术新材料新科技的不断产生和高效施工方法的出现,未来的高层建筑结构将向着更合理的结构设计体系和考虑环保、节能、舒适、多功能等可持续发展观念的人性化设计方向发展,文章对高层建筑结构的设计特点进行了分析,从结构体系方面论述了现有各种结构承重体系及其特点,最后提出了高层建筑结构体系的发展趋势.     

猪瘟病毒E2抗原在不同酶标板上包被效果的比较

为比较杆状病毒表达的猪瘟病毒(CSFV)E2抗原在不同酶标板上的包被效果,本研究应用2 Rg/mL的CSFV E2分别包被Nunc Maxisorp,Cosar StripWell和JET FEP-101-896 3种酶标板,以Flyer Liquid Plate Sealer(FLPS)进行封闭,通过比较猪瘟阳性血清的OD_450值,筛选包被性能最佳的酶标板.对FLPS、含10%FCS的PBST和含1 % BSA的PBST的封闭效果进行比较.并比较 FLPS在相同抗原条件下重复使用2次和3次对于CSFV阳性血清检测结果的影响.结果显示,在CSFV E_2抗原包被的3种酶标板上,CSFV阳性血清的OD_450nm,值均存在显著差异(p<0.05),其中以Cosar酶标板OD41,值最高;在Costar板上,3种封闭液间及FLPS重复使用对于CSFV阳性血清的检测结果无显著差异(p>0.05).     

Constitutive Model for Negative Simple-sheared Soil-concrete Interface

Negative shear property of soil-concrete interface is one critical issue in civil engineering. According to negative simple shear tests of soil-concrete interfaces with various water content, quantitative analysis on changes of shear strength, friction angle and cohesion force of negative sheared interface against positive shear experience were conducted. Several empirical formulae were proposed for above changes, and critical positive shear ratio was put forward. Based on improved stress-strain equation, mathematical model for tangent modulus of negative sheared soil-concrete interface was established. This new model consists ten parameters which can be determined by simple shear test. Process for determining these ten parameters was presented, and empirical values of them were obtained. Simulations for stress-strain curves of soil-concrete interface were carried out, and good ability of the model was found.     

Analysis on wall slip phenomenon andcharacteristics of sewage sludge

Wall slip of sewage sludge and possible slip in fluencing factors are studied experimentally by using a rotational rheometer with parallel plate fixtures and by high speed camera．The technique involves placing a straight line marker to monitor wall slip, checking the gap dependence of the stress-strain data and studying the time-stress data trend of strain stepped scanning. In the shearing flow it is found that, for sewage sludge of water content 80%, as the strain amplitude increases, the stress data starte to diverge at a certain strain amplitude, indicating that wall slip occurs. Meanwhile, it has been utilized for studying the critical shear stress and calculating the slip velocity, and the formulation of shear stress and slip velocity are fitted. But for sewage sludge of water content 90%, these curves are superimpose, indicating no slip occurs．While scanned sewage sludge water content 80% at different shear rates in 5 s and 60 s, it is found that under 5 s and 60 s, when the shear rate is greater than 10 s-1 and 0.5 s-1 respectively, peak appeas in time-stress curves, i.e. slip occurs. Therefore, concentration, shear rate and time have influence on wall slip.     

Simulation and analysis of mechanics of coal and gas delay outburst

The buried box girders in the mountain city sewage pipeline system would be turned into simple-supported girders because of the removal of the foundation caused by landslide.This change of supporting would result in the failure risk of pipeline structure.The static properties of the buried box girders with small depth-to-span ratio in simple-supported condition are experimentally analyzed.The failure pattern,shear behavior and shear lag effect of the buried box girders in simple-supported condition are studied.The shortages in the present design codes for the calculation of shear capacities of the box girders are also discussed.It is shown that under the vertical uniformly distributed load,the crack distribution of the box girders is uniform,and no major critical diagonal crack is formed,and the box girders lose the bearing capacity in the form of concrete diagonal rod crushing.As the main shear-bearing components,the stirrups devote much to shear capacity of the box girder after concrete cracking.The strains of the longitudinal rebars are affected by those factors such as the redistribution of internal force and cracks,so only few areas of the box girders show the shear lag effect.The change of supporting form leads to the premature cracking of concrete and affects the serviceability of the sewage pipeline.     

土石坝坝体复合土工膜防渗斜墙的受力分析

在土石坝坝体防渗中,土工膜有时作为一种防渗材料铺设在坝体的上游坡中,以保护坝体的安全运行.在试验基础之上,重点分析复合土工膜的主要力学特性,并结合一座建在深厚覆盖层上的复合土工膜防渗土石坝,对其进行非线性结构分析,着重研究复合土工膜与坝体结构面之间的剪切变形特性.试验结果表明,复合土工膜与坝体粗粒料垫层结构面的剪应力-剪应变关系为应变软化型.计算结果表明,在现有可能不利条件下,该坝坝体、坝基及复合土工膜的应力变形均在合理可控范围之内,大坝结构安全能够满足要求.