Early detection of reproduction deficits and the compensatory potential of enhancement stocking for vendace,Coregonus albula,fisheries in German lakes

Enhancement stocking is a widespread but rarely evaluated practice in German vendace, Coregonus albula L. fisheries, which is precautionarily carried out to buffer yield fluctuations. However, it is assumed that stocking of larval vendace can elevate year‐class strength only in the presence of substantial reproductive deficits, which so far cannot be detected prior to the spring time period when stocking is conducted by fisheries managers. Simple measures for the early quantification of natural reproduction were tested, and the efficiency of larval enhancement stocking in a lake with strong reproduction deficits was analysed. Analysis in four lakes over 3 years revealed a significant positive correlation between standardised catches of vendace larvae caught with pump‐driven illuminated traps in spring and the abundance of young‐of‐year (YoY) vendace in the following autumn, whereas standardised catches of spawners were insufficient to forecast YoY recruitment. In a lake with low natural vendace reproduction, stocked vendace contributed 73–100% of year‐class strength and fisheries yield. Accordingly, enhancement stocking can efficiently compensate for reproduction deficits, and the simple larvae sampling method may facilitate early detection of these deficits, which would allow fisheries managers to respond accordingly through larvae stocking.     

不同烘烤条件下烤烟纤维素的近红外光谱检测模型研究

为探索不同烘烤条件下烤烟纤维素含量近红外光谱检测模型,采用偏最小二乘回归法(PLS)对不同烘烤条件下的共85个样品,分别基于全部波长建立模型。常规烘烤时,定标集r=0.9949,RMSE=0.1122;交叉验证集r=0.9234,RMSE=0.4636;预测集r=0.8982,RMSE=0.6963。低温烘烤时,定标集r=0.9811,RMSE=0.3279;交叉验证集r=0.9456,RMSE=0.5290;预测集r=0.9938,RMSE=0.1608。高温烘烤时,定标集r=0.9128,RMSE=0.4381;交叉验证集r=0.8215,RMSE=0.6162;预测集r=0.9743,RMSE=0.1986。结果表明,采用偏最小二乘法预测不同烘烤条件下烤烟纤维素含量是可行的。     

黄土高原沟壑区坡耕地表层土壤抗剪强度影响因素分析

以淳化坡耕地为研究对象,在人工模拟降雨条件下,设计降雨强度分别为0.5、1.0、1.5、2.0、2.5 mm/min,降雨历时40 min,设计坡度分别为5°、8°、11°、15°、20°,分析了影响黄土高原沟壑区坡耕地表层土壤抗剪强度的3个主要因素:含水量、雨强及坡度.结果表明,降雨结束后,随着表层土壤含水量的降低,抗剪强度会随之增加,相关性较好;雨强对抗剪强度影响不大;坡度较小时抗剪强度会随坡度增加而降低,当坡度增加到15°以上时,随坡度增加抗剪强度随之增加.     

Effects of Heterotrophic and Autotrophic Bacteria on the Stability of Aerobic Granular Sludge

The characteristics of granules of heterotrophic and autotrophic bacteria were studied. The autotrophic granules were characterized by smaller granule size, higher density, higher concentration of extracellular polymeric substances (EPS) and weaker strength compared with the heterotrophic ones. The diameter and density of autotrophic granules were changed in the same fashion, resulting in stable granules, and the heterotrophic granule, however, grew up with the increase of diameter and the decrease of density. According to the strength analysis, it is proposed that in the autotrophic system, the balance between EPS and porosity is the main reason for the long term stability. However, the balance could not be obtained in the heterotrophic system and that the operational conditions could not control the overgrowth of filamentous bacteria was the reason for the instability.     

N式砌块砌体受剪性能试验研究

对30个N式砌块砌体抗剪试件(其中未灌孔试件6个,灌孔试件24个)进行了受剪力学性能试验研究,了解了N式砌块砌体的破坏形态及破坏机理.试验结果表明,灌孔N式砌块砌体的受剪开裂荷载与极限荷载的比值随灌孔率的不同分别为:半灌孔试件77%~82%、全灌孔试件54%~59%.随着灌孔混凝土面积的增大,N式砌块砌体表现出越来越好的延性.未灌孔N式砌块砌体的抗剪强度平均值比砌体规范抗剪平均强度公式计算值高出11%,半灌孔N式砌块砌体的抗剪强度平均值比砌体规范平均强度计算值高出5%,全灌孔N式砌块砌体的抗剪强度平均值比砌体规范平均强度计算值高出74%~106%.     

K326烟叶在密集式烤房条件下121烘烤工艺初探

根据卷烟工业开发浓香型特色优质烟叶的要求,为探索烤烟K 326品种在密集式烤房条件下的烘烤工艺,解决烟叶在现有烘烤工艺下烤黄不烤香,烟叶含青量过大,淀粉含量过高等问题,在烤烟三段式烘烤工艺的基础上,调整变黄期干湿球温度和变黄程度指标,对K 326烟叶烘烤工艺进行了改良。结果表明,改良后的烘烤工艺能降低淀粉和叶绿素含量,总糖含量提高6.64%,还原糖含量提高6.26%,增加了中上等烟叶比例,提高了产值,烟叶质量变佳,工业可用性得到提高。     

固化风沙土无侧限抗压强度试验研究

在应用固化剂稳定风沙土做底基层试验研究中,从提高无侧限抗压强度方面对固化风沙土强度进行试验研究。击实试验结果表明:掺8%固化剂风沙土最大干密度要比纯风沙土最大干密度增大很多而最优含水率略有下降。无侧限抗压强度试验结果表明:风沙土无侧限抗压强度随固化剂掺量增加强度提高不显著,那么在固化风沙土中掺入20%-50%砂砾后,固化风沙土和砂砾混合料无侧限抗压强度提高很显著。在固化剂掺量小于8%、砂砾掺量50%的固化混合料试验中,砂砾和风沙土混合料强度随固化剂掺量的增加成线性增加。根据实际工程情况,调整砂砾和固化剂二者掺量关系,固化砂砾和风沙土混合材料既能满足高等级公路底基层、基层强度要求又能达到降低成本、改善材料性能的目的。     

冷等离子体处理对竹材胶合性能的影响研究

[目的]研究冷等离子体处理对竹材胶合性能的影响。[方法]采用氧气,氮气,氨气和氩气这四种冷等离子体分别对竹材进行处理,比较处理前后竹材接触角和胶合强度的变化。[结果]氧冷等离子体处理可提高竹材胶合强度25%-30%,冷等离子处理过程非常迅速且有效,但接触角变化并不大。[结论]冷等离子体处理导致木材胶合强度增加。     

竹材磨削表面粗糙度与胶合强度关系的研究

【目的】分析影响竹材磨削表面粗糙度的因素以及表面粗糙度与胶合强度的关系,为竹材胶合加工工艺的选择提供参考依据。【方法】采用探针法等,测定不同粒度（60,80,100,150和180目）砂带磨削加工后竹材的表面粗糙度、表面自由基数量和表面接触角,对磨削加工试件进行胶合强度试验,分析表面粗糙度、表面自由基和表面接触角等对胶合强度的影响。【结果】磨削砂带粒度过小和过大时,胶合强度均较低。本试验条件下,砂带粒度为100目时,磨削竹材的胶合强度最高（7.19 MPa）,表面润湿性也最好。此时,表面粗糙度评价指标轮廓算术平均偏差（Ra）、微观十点不平度（Rz）和轮廓微观不平度平均间距（Sm）分别为7.2,50.7和130.8 μm,表面自由基数量为3.3×10⁴ g^-1,表面接触角约15°。【结论】竹材胶合加工表面磨削时选择100目的砂带较为合理。     

半干旱区玉米降解地膜覆盖栽培综合效应研究

针对吉林省西部半干旱区降水量少,特别是玉米生育期降水分布不均,玉米产量稳定性差等问题,采用降解地膜覆盖、不覆盖、普通地膜覆盖3种栽培模式,对土壤温度、水分、土壤理化性状、土壤微生物及玉米产量的影响进行研究。结果表明,降解地膜覆盖具有显著的增温保墒作用,可改善土壤物理性状,增加土壤速效养分,促进土壤微生物的活动,提高玉米的产量。降解地膜覆盖较不覆盖地膜增产14.51%;使用的降解地膜在7月下旬可分解至6级,重量减少66.35%,降低了地膜对土壤环境的污染程度。