淡水石首鱼幼鱼外部形态与内部解剖学特征

世界上275种石首鱼类中仅有极少数终生生活在淡水中,北美洲特有的淡水石首鱼(Aplodinotus grunniens)是其中一种,其形态学和内部解剖学特征研究对探讨石首鱼类的系统发育和进化具有重要价值。本研究较系统地对淡水石首鱼幼鱼的外部形态学可量可数性状进行测量,对内部主要器官结构及矢耳石特征进行解剖学观察。结果显示:除了吻端、颐部和峡部外,淡水石首鱼体被两种鳞片,头部两侧的鳃盖及眼睛周边覆盖小圆鳞,头后身体包括喉部均被栉鳞,且在头背交界处存在两种鳞片的过渡类型;侧线鳞从头后一直延伸至尾鳍的1/2处。腹鳍第一鳍条膜稍延长形成特有的鳍丝。黏液孔主要分布在颐部,为五孔型;具有犬牙状的颌齿和咽齿,所有齿尖均向口腔内部方向弯曲,上咽齿盘分为左右对称的2个咽齿盘,而下咽齿盘愈合为一体;消化道主要由口咽腔、较短的食道、卜形胃、具有2个弯转的肠道及肛门组成,在胃与肠交界处具有7个环状排列的指状幽门盲囊。矢耳石的形态特征与中国的黄唇鱼相似。基于外部形态学和内部解剖学特征,讨论分析了淡水石首鱼与中国石首鱼物种的亲缘关系。淡水石首鱼归属于低级底栖肉食性鱼类,这与其特定的生态习性和摄食特性等相符合。本研究旨在为中国淡水石首鱼人工驯养和紫黑翼蚌的规模化寄生繁育奠定基础,也为探讨石首鱼类在海淡水区域地理格局演化提供了基础资料。     

Dietary requirements for leucine,isoleucine and valine (branched‐chain amino acids) by juvenile red drum Sciaenops ocellatus

The objective of this study was to determine the minimum dietary requirements of the branched‐chain amino acids (BCAAs: leucine [Leu], isoleucine [Ile] and valine [Val]) for juvenile red drum, Sciaenops ocellatus. This was accomplished by conducting three independent 49‐day feeding trials with juvenile red drum. Experimental diets were prepared by supplementing a basal diet containing 370 g/kg crude protein from red drum muscle and crystalline amino acids with incremental levels of Leu (9.0, 13.0, 17.0, 21.0, 25.0 and 29.0 g/kg of dry diet), Ile (5.0, 8.0, 11.0, 14.0, 17.0 and 20.0 g/kg of dry diet) and Val (6.8, 8.0, 9.2, 10.4, 11.6, 12.8 and 14.0 g/kg of dry diet). Fish were fed to apparent satiation twice daily in each trial, after which growth performance parameters were calculated and body composition and concentrations of BCAAs in plasma were analysed. Incremental levels of dietary Leu, Ile and Val significantly affected weight gain, feed efficiency and protein retention. Analyses of the weight gain data using a broken‐line regression model estimated the minimum Leu, Ile and Val requirements for maximum growth of juvenile red drum to be 15.7 ± 1.7 g/kg (±95% confidence interval), 11.1 ± 2.3 g/kg and 12.4 ± 0.6 g/kg of dry diet, respectively.     

平衡鼓间隙对首级叶轮前泵腔压力及多级泵轴向力的影响

平衡鼓的轴向力平衡能力是多级离心泵发生故障并影响其寿命的关键因素。该文采用数值模拟方法,在多级泵的外特性、平衡管内压力和泄漏量的数值计算结果与试验结果基本一致的基础上,研究了平衡鼓间隙泄漏量变化对首级叶轮前泵腔的压力分布、首级叶轮及整个叶轮轴向力的影响。研究结果表明:首级叶轮前泵腔中的漩涡区是腔体内压力变化的主要原因。当平衡鼓间隙由0增大到0.5 mm时,首级叶轮的轴向力在间隙为0时最大,在间隙为0.3 mm时最小,其最小值为最大值的20.6%;整个叶轮所受轴向力随着平衡鼓间隙增大呈先减小后增大的趋势。无量纲化的平衡鼓间隙面积大于6.6×10-3时,由于平衡鼓前后压差较小,已无法有效平衡轴向力,在此范围轴承发生断轴的风险较大。该研究可为多级泵平衡鼓设计提供参考。     

基于EDEM的马铃薯收获机分离输送装置仿真分析

为了实现提高马铃薯收获效率并减少其机械损伤,关键在于优化滚筒式马铃薯收获机分离输送装置的运动参数,包括滚筒筛转速、切削角度和行进速度.为此,建立了土壤颗粒的仿真模型、马铃薯颗粒的仿真模型和马铃薯收获机分离输送装置的仿真模型,通过EDEM软件仿真土壤和马铃薯颗粒的分离输送试验并收集数据;运用Design-expert软件...     

Effect of Chitosan Coating Enriched with 6-gingerol on Red Drum Fillets Quality and Shelf Life during Refrigerated Storage

The effect of chitosan coating enriched with 6-gingerol on the quality and shelf life of red drum fillets during refrigerated storage was investigated in this study. Samples were applied with chitosan coating (CH), 6-gingerol (GI), and chitosan coating with 6-gingerol (CH+GI) before storing at 4°C for 20 days. The data in this study showed that treatment with CH+GI could significantly decrease pH value, K-value, thiobarbituric acid value, and total volatile basic nitrogen in red drum fillets during refrigerated storage. The counts of microorganisms, such as Enterobacteriaceae, psychrotrophic, mesophilic bacteria, and lactic acid bacteria, were also significantly lower in the CH+GI group compared with those in the CH and GI groups. Moreover, the combination of chitosan coating and 6-gingerol was more effective in relieving the deterioration of tissue texture and sensory characteristics in the red drum fillets. In addition, the results suggested that chitosan coating and 6-gingerol had a synergistic effect on the quality improvement of red drum fillets. This work demonstrates that chitosan coating enriched with 6-gingerol may be a promising natural preservative for red drum during refrigerated storage.     

滚筒式堆肥反应器通风搅拌系统设计与试验

针对有机废弃物堆肥过程中物料溶氧效率低导致的堆体起温速率慢、发酵不彻底等问题,设计了一种高效堆肥通风搅拌系统,该系统由分段式通风系统和组合式搅拌装置构成,通过对两个主要装置进行理论设计和DEM-FEM耦合仿真,〖JP3〗实现堆肥通风和搅拌工艺优化。结果显示,通风系统中的最大应力出现在通风管上,为13.064MPa,最大形变量为0.038126mm,搅拌装置中最大应力出现在抄板上,为190.31MPa,最大形变量为0.34417mm,符合设计要求。在此基础上,以食物垃圾和梧桐叶为原料,进行为期14d的堆肥试验,监测堆肥过程中关键参数变化并测定发酵产物相关指标,完成通风搅拌系统性能验证试验。试验结果表明：使用该通风搅拌系统的滚筒式堆肥反应器,其内部堆体温度在3d时达到53.34℃,堆肥过程中堆体最高温度可达69.56℃,堆体高温期（大于50℃）可持续6d以上;试验结束后其产物含水率降至27.21%、pH值升至8.4、种子发芽指数最高可达131.4%,符合有机肥料测定标准(NY/T 525—2021),滚筒反应器运行成本仅65.51元/t。     

转筒内D型二元颗粒物料滚落模式的径向分离

针对D型二元颗粒物料在转筒内的分离问题,以粘土颗粒和木制颗粒组成的物料为对象,采用离散单元法模拟了滚落运动模式下物料在转筒内的运动与分离过程。通过颗粒接触数定义物料混合指数,并结合Hong的渗流与凝聚竞争理论定量分析了物料的径向分离。结果表明:滚落运动模式下物料在转筒截面上分为平流层与活动层两部分,颗粒之间的分离运动发生在活动层;颗粒密度差异引起凝聚作用,使木制颗粒向转筒内壁分散而粘土颗粒向中心聚集,物料形成"月亮模式"分离形态;通过配置2种颗粒的半径可引入渗流机理,当渗流作用与凝聚作用相互平衡时,可避免物料发生径向分离;渗流机理的引入不受转筒尺寸的影响。     

纵轴流复脱分离装置设计与试

为了研究切流与纵轴流组合式脱粒分离装置的作业性能,在纵轴流脱粒分离清选试验台上,对钉齿滚筒、矩形齿滚筒和钉齿-短纹杆板齿组合式滚筒进行了台架试验,比较其夹带损失率、未脱净率、脱出物轴向分布规律、含杂率和功耗.试验结果表明,3种复脱滚筒在脱粒小麦时夹带损失率小,脱净率高;相对钉齿滚筒及矩形齿滚筒而言,钉齿-短纹杆板齿组合式滚筒脱出物轴向分布均匀,含杂率和功耗较低.     

五种理化因子对眼斑拟石首鱼苗种的影响

报道了眼斑拟石首鱼苗种对盐度、有效氯、高锰酸钾、硫酸铜耐受力的实验,测定了它的呼吸耗氧量和窒息点：缺氧浮头时的溶氧值为1．86mg／L,窒息点范围为0．79～0．38mg／L。实验表明：有效氯毒性极强,高锰酸钾次之,CuSO4·5H2O较弱。采用1×10(－6)以下的CuSO4·5H2O处理眼斑拟石首鱼鱼苗是安全的。     

带直扬料板回转筒内秸秆碎料运动与混合机理研究

为研究扬料板对实验室级回转筒内秸秆碎料发酵热均匀化速度的影响,需研究筒内二元秸秆碎料颗粒的混合速度。基于图像分析,建立了研究二元秸秆碎料颗粒混合度Imix及完全混合时间Tc的方法,并用Visual Studio编写了分析软件。依据实验室级回转筒设计实验台,采用完全实验、分析软件和正交分析法,研究了直扬料板对Tc的影响。结果表明:对实验室级回转筒而言,在对Tc的影响上,板长大于板数,两者数量级相同,均表现显著,并相互耦合;宏观效应曲线上,Tc随板长增加类余弦函数规律变化,随板数增加类指数函数规律变化;Tc向"单+长板"和"多+中长板"两级化降低,向"多+短板"和"多+长板"两级化升高,4块板55%筒体半径长度扬料板情况下混合最快。不当的扬料板选择,反而会降低筒内料发酵热的均匀化速度,选用扬料板时,应采用"多+中长板"方案。最后,基于摄像结果分析了颗粒的运动模式、扬料板的作用过程、扬料板作用下的物料混合机理,归纳总结了不同长度/数量的扬料板作用下的颗粒运动模式,完成实验室级回转筒内物料运动模式的分解、定性研究。对于工业级回转筒,可参考本文所提出方法进行实验研究。