Wind Tunnel Test for Section Model of Caiyuanbai Bridge Over Yangtse River

With the development of modern construction technique and the application of new material,arch bridges which progress towards small rigidity,long span and light weight,what's more is that long span bridge's rigidity under construction is much less than that in use stage.So it is very necessary to study the aerodynamic characteristics of long span bridge.The regularity of the three dimensional static component forces coefficient varying with attack angle and the girder's flutter properties of Caiyuanbai Bridge over Yangtse River are investigated with segmental molding's static wind-tunnel test and segmental molding's dynamic wind-tunnel test.Eight derivatives of the girder are also identified from the segmental molding's dynamic wind-tunnel test.Finally the assessment to wind resistant properties of the bridge is given based on detailed analysis of the test results.The conclusion which gets from analysis can provide an suggestion to design and construction this kind bridge.     

Quantifying the effects of bycatch reduction devices in Queensland''s (Australia) shallow water eastern king prawn (Penaeus plebejus) trawl fishery

This study presents results from an experimental 10-day research charter that was designed to quantify the effects of (a) a turtle excluder device (TED), (b) a radial escape section bycatch reduction device (BRD) and (c) both devices together, on bycatch and prawn catch rates in the Queensland shallow water eastern king prawn (Penaeus plebejus) trawl fishery. The bycatch was comprised of 250 taxa, mainly gurnards, whiting, lizard fish, flathead, dragonets, portunid crabs, turretfish and flounders. The observed mean catch rates of bycatch and marketable eastern king prawns from the standard trawl net (i.e., net with no TED or BRD) used during the charter were 11.06 kg/hectare (ha⁻¹) (S.E. 0.90) swept by the trawl gear and 0.94 kg ha⁻¹, respectively. For the range of depths sampled (20.1–90.7 m), bycatch rates declined significantly at a rate of 0.14 kg ha⁻¹ for every 1 m increase in depth, while prawn catch rates were unaffected. When both the TED and radial escape section BRD were used together, the bycatch rate declined by 24% compared to a standard net, but at a 20% reduction in marketable prawn catch rate. The largest reductions were achieved for stout whiting Sillago robusta (57% reduction) and yellowtail scad Trachurus novaezelandiae (32% reduction). Multidimensional scaling and analysis of similarities revealed that bycatch assemblages differed significantly between depths and latitude, but not between the different combinations of bycatch reduction devices. Despite the lowered prawn catch rates, the reduced bycatch rates are promising, particularly for S. robusta, which is targeted in another fishery. Prawn trawl operators are not permitted to retain S. robusta and the devices examined herein offer the potential to significantly reduce the incidental fishing mortality that this species experiences.     

草鱼出血病鱼主要器官组织的超薄切片观察及感染力的比较

草鱼出血病是一种严重的病毒性疾病,它会引起草鱼大批死亡。已有报告指出,在病鱼肾组织的超薄切片中观察到病毒粒子的存在,并认为肾脏是草鱼出血病病毒侵袭是严重的器官。在制备草鱼出血病组织疫苗时仅取病鱼的肝、脾、肾和肌肉组织,肠道组织往往弃之不用。为了进一步确定病     

DNA原位杂交技术在花粉管通道法遗传转化途径研究中的应用

本文对DNA原位杂交技术在研究植物花粉管通道法遗传转化途径中的应用进行了综述,内容涉及花粉管通道法遗传转化途径问题的研究方法、影响原位杂交及其检测效果的技术关键等。笔者根据本人在研究工作中的应用实践,对原位杂交技术中所涉及到的组织切片方法及切片厚度、载玻片处理、探针长度及其标记、杂交信号的检测等关键技术环节着重进行了比较和讨论。     

室温下鸡蛋涂膜保鲜技术研究

通过对壳聚糖溶液、壳聚糖和氢氧化钙复合溶液、液体石蜡3种保鲜剂在常温下对鸡蛋的保鲜效果进行对比,结果表明：经过35d的储藏时间,发现氢氧化钙与2%壳聚糖溶液复合保鲜剂和液体石蜡保鲜剂的保鲜效果相当,好蛋率、失重率等指标均优于其他处理组;保鲜剂成膜的致密性和阻气性是影响鸡蛋储藏期的关键,而非传统观念上的抑菌性。     

西气东输二线西段水土流失动态监测与分析

[目的]动态监测西气东输二线工程中重点地段、重点对象的水土流失状况,为后续长输管线水土保持动态监测提供一定的理论支撑和实践指导。[方法]定位观测与遥感监测方法相结合,在天山山地区,吐哈盆地及河西走廊戈壁沙漠区这3处重点地段进行监测。[结果]工程建设造成了大量新增水土流失,建设过程中新增加的水土流失量为1.61×106 t;在新增加的土壤流失量中,管道作业带流失量占总流失量的93.68%,是施工过程中重点防治区域。[结论]工程建设加剧了项目区水土流失。     

甘肃中部引黄灌区枸杞施肥管理与土壤养分状况调查分析

通过对景泰县草窝滩镇枸杞幼龄园(1～4年生)和盛果期成龄园(5～8年生)施肥管理现状调查,并结合其20～40 cm土壤养分测试,分析目前该区构杞养分管理中存在的问题及不同龄期枸杞园土壤养分特征.结果表明,该区枸杞养分管理中注重有机肥投入,但施用量不足;化肥施用中重氮素、磷素,轻钾素现象较为普遍.全量养分中有机质和全氮含...     

Effect of external compressive load on tangential strain behavior in Japanese larch log cross sections during radio-frequency/vacuum drying

This study investigated the effect of a compressive load of 0.092 MPa on the history of the tangential strains in Japanese larch (Larix leptolepis Gordon) log cross sections subjected to external compressive load during radio-frequency/vacuum drying. The external compressive load of 0.092 MPa played a role in inducing cracking in the outer zone of the log cross section, combining with other tensile strains. However, it also played a role in reducing the heart checks in the core of log cross section when exerted on the cross section of log cross section.     

砼深受弯构件及圆形截面构件受剪承载力

结合 GBJ10 - 89混凝土结构设计规范修订课题 ,提出了混凝土深受弯构件和圆形截面偏压构件抗剪承载力的计算方法 .这些方法与试验资料吻合良好 ,并与矩形截面一般受弯构件的计算方法在一定程度上得到了统一 .