Study on damage mechanism and damage distribution of the rear plate under impact of debris cloud

The debris cloud generated by the hypervelocity impact(HVI)of orbiting space debris directly threatens the spacecraft.A full understanding of the damage mechanism of rear plate is useful for the optimal design of protective structures.In this study,the hypervelocity yaw impact of a cylindrical aluminum projectile on a double-layer aluminum plate is simulated by the FE-SPH adaptive method,and the damage process of the rear plate under the impact of the debris cloud is analyzed based on the debris cloud structure.The damage process can be divided into the main impact stage of the debris cloud and the structural response of the rear plate.The main impact stage lasts a short time and is the basis of the rear plate damage.In the stage of structure response,the continuous deformation and inertial motion of the rear plate dominate the perforation of the rear plate.We further analyze the damage mechanism and damage distribution characteristics of the rear plate in detail.Moreover,the connection between velocity space and position space of the debris cloud is established,which promotes the general analysis of the damage law of debris cloud.Based on the relationship,the features of typical damage areas are identified by the localized fine analysis.Both the cumulative effect and structural response cause the perforation of rear plate;in the non-perforated area,cratering by the impact of hazardous fragments is the main damage mode of the rear plate.

An enhanced almost blank sub-frame management for efficient elCIC in non-uniform HetNets

A new enhanced inter-cell interference coordination （elCIC） is adopted for managing almost blank sub-frame （ABS）,which jointly exploits the time, frequency and power dimensions to improve the resource utilization. In particular, a non-uniform two tier heterogeneous network （ HetNet） is considered, where the pico cells are located close to the macro cell and the number of users in each pico cell is different. To alleviate the interference caused by the co-channeldeployment,the macro cells employ low power ABS （LP- ABS）, and the resource blocks （RBs） are divided into twoparts during an ABS. One is exclusively reserved for macro cell users ad the other is reserved for pico cell users. Themacro cells are allowed to use different percentages of RBs and different powers for their own transmission during the LP- ABS. The user association,resource allocation,ABS proportion,the frequency band partition parameter and the transmission power of macro cells are considered, aiming at maximizing the proportional fairness utility of the system. An iterative algorithm is also proposed and simulation results demonstrate that the proposed algorithm can improve both the system throughput and user fairness compared with the existing schemes.

Comparative study on wheel-rail dynamic interactions of side-frame cross-bracing bogie and sub-frame radial bogie

Improving freight axle load is the most effective method to improve railway freight capability; based on the imported technologies of railway freight bogie, the 27 t axle load side-frame cross-bracing bogie and sub-frame radial bogie are developed in China. In order to analyze and compare dynamic interactions of the two newly developed heavy-haul freight bogies, we establish a vehi- cle-track coupling dynamic model and use numerical calculation methods for computer simulation. The dynamic performances of the two bogies are simulated separately at various conditions. The results show that at the dipped joint and straight line running conditions, the wheel-rail dynamic interactions of both bogies are basically the same, but at the curve negotiation condition, the wear and the lateral force of the side-frame cross-bracing bogie are much higher than that of the sub-frame radial bogie, and the advantages become more obvious when the curve radius is smaller. The results also indicate that the sub- frame radial bogie has better low-wheel-rail interaction characteristics.

Effects of rearing system and antibiotic treatment on immune function,gut microbiota and metabolites of broiler chickens

Background:In China,cage systems with a high space utilization have gradually replaced ground litter systems,but the disease incidence of chickens in cages is higher.Broilers in the ground litter pens may be stimulated by more environmental microbes during the growth process and show strong immune function and status,but knowledge of which microbes and their metabolites play an immunomodulatory role is still limited.This study aimed to explore the differences and correlations in the immune function,gut microbiota and metabolites and the importance of gut microbiota of broilers raised in cages and ground litter pens.Methods:The experiment involved a 2×2 factorial arrangement,with rearing systems(cages or ground litter pens)and antibiotic treatment(with or without broad-spectrum antibiotics in drinking water)as factors.Results:The results showed that,compared with the cage group,the ground litter broilers had stronger nonspecific immune function(Macrophages%and NO in blood),humoral immune function(IgG in blood,LPS stimulation index in ileum)and cellular immune function(T%,Tc%,ConA stimulation index and cytokines in blood).Antibiotic(ABX)treat-ment significantly reduced nonspecific immune function(Macrophages%and NO in blood,iNOS and Mucin2 mRNA expression in ileum),humoral immune function(IgG in blood and sIgA in ileum)and cellular immune function(T%and cytokines in blood,Th and Tc ratio,TLRs and cytokines mRNA expression in ileum).Furthermore,the ground litter broil-ers had higherαdiversity of microbiota in ileum.The relative abundance of Staphylococcus,Jeotgalicoccus,Jeotgalibaca and Pediococcus in the ileum of ground litter broilers were higher.ABX treatment significantly reduced theαdiversity of ileal microbiota,with less Chloroplast and Mitochondria.In addition,the levels of acetic acid,isobutyric acid,kynurenic acid and allolithocholic acid in the ileum of ground litter broilers were higher.Spearman correlation analysis showed that Jeotgalibaca,Pediococcus,acetic acid,kynurenic acid and allolithocholic acid were related to the immune function.Conclusions:There were more potential pathogens,litter breeding bacteria,short-chain fatty acids,kynurenine,allolithocholic acid and tryptophan metabolites in the ileum of broilers in ground litter pens,which may be the reason for its stronger immune function and status.

Influence of Curve Geometric Parameters on Curving Performance of Sub-frame Radial Bogie

Based on the theory of vehicle-track coupling dynamics,the coupling dynamic model of the freight car mounted with the sub-frame bogies and the numerical model of curved track were established,utilizing the fast numerical integration method,the curving performance of the vehicle was simulated to study the influence of the curve geometric parameters such as curve radius,transition curve length and superelevation of outer rail on the wheel-rail dynamic interaction.The simulation results indicate that:(1)Increasing the curve radius can decrease the wheel-rail wear,but the effect will weaken while the curve radius is greater than 800m.(2)If the transition curve length is less than 30m,vibrations will appear at the transition-circle connecting point,and the smaller the transition length,the bigger the vibrations,the worse the wheel-rail wear,but when the length is bigger than 50m,its further variation has very little effect on wheel-rail wear.(3)The superelevation of outer rail can affect the distribution and difference of the inner and outer wheel-rail forces,and too large deficient or excessive superelevation will worsen the wheel-rail wear either.However,an appropriate deficient superelevation of outer rail(e.g.<20mm)is helpful to reduce the wheel-rail wear,which is consistent with the engineering practice of settling a certain deficient superelevation value.

Performance of Two Food Substrates in the Mass Rearing of Bactrocera dorsalis Hendel (Diptera: Tephritidae)

The fruit fly Bactrocera dorsalis Hendel is a major constraint to mango production in Burkina Faso. The objective of this study was to evaluate the performance of two types of food substrates in optimizing the mass rearing of B. dorsalis larvae. For this purpose, 200 eggs of B. dorsalis were divided into four batches of 50 eggs and incubated in Petri dishes containing the different food substrates (Diet 1 and Diet 2). This method was used to evaluate the rate and duration of egg hatching, as well as the development time of the different larval stages. In addition, 1200 pupae divided into four batches of 300 pupae, contained in PVC tubes, were placed inside the rearing cages to monitor the emergence of B. dorsalis. Ten pairs of B. dorsalis were placed in rearing cages and fed with Enzymatic Yeast Hydrolysate and sugar to evaluate the fecundity of female flies and the survival of both sexes. The developmental cycle length in Diet 1 and Diet 2 was 23.03 days and 23.24 days, respectively. Fecundity duration ranged from 57.75 ± 2.29 to 109.81 ± 3.81 days for females from Diet 1 and Diet 2, respectively. The pupal hatching rate varied significantly (P B. dorsalis, but the spawning index was 4 times higher with Diet 1. Most of the components of Diet 1 are available on the local market and are cheaper. Thus, we recommend the use of Diet 1 for B. dorsalis larvae mass rearing.

维生素C对禁食黄颡鱼抗氧化能力和肌肉品质的影响

【目的】研究添加不同浓度维生素C对禁食暂养黄颡鱼(Pelteobagrus fulvidraco)抗氧化能力和肌肉品质的影响,为提升鲜活黄颡鱼耐运性和肌肉品质提供理论依据。【方法】随机将黄颡鱼分为4组:T0-0(0 mg/L V_(C),暂养0 d)、T0-5(0 mg/L V_(C),暂养5 d)、T10-5(10 mg/L V_(C),暂养5 d)、T30-5(30 mg/L V_(C),暂养5 d),每组40尾鱼,检测血清、肌肉的抗氧化物质以及肌肉品质指标。【结果】T5-0组黄颡鱼血清中GSH-PX、CAT、GSH活性以及MDA浓度,肌肉中CAT、GSH活性和MDA浓度显著低于T1-0组(P<0.05);其纤维结构变得紧密,pH下降,白度增加,持水力增加,肌肉品质指标显著升高(P<0.05)。与T0-5及T30-5组相比,T10-5组血清中SOD、CAT、GSH、GSH-PX活性显著较高(P<0.05),MDA浓度较低;肌肉中SOD、GSH活性与血清中结果变化相同;持水力进一步增加。在质构方面,T10-5组剪切力、硬度、弹性、咀嚼性、黏性均高于T0-5组及T30-5组。【结论】添加10 mg/L的V_(C)能进一步显著提高黄颡鱼的抗氧化能力和肌肉品质(P<0.05),但30 mg/L V_(C)添加不利于黄颡鱼肌肉品质的提升,甚至对其产生负面影响。

家庭功能和积极应对方式对孤独症谱系障碍儿童父母养育倦怠的影响

目的 分析家庭功能和积极应对方式对孤独症谱系障碍(ASD)儿童父母养育倦怠的影响。方法 采用便利抽样法,选取2022年6月至2023年5月在东莞市妇幼保健院确诊的ASD儿童的父母60名作为试验组,选取健康正常儿童的父母60名作为对照组,比较两组家庭功能问题;Pearson相关分析试验组家庭功能、父母养育倦怠、积极应对方式的关系;中介效应检验采用Bootstrap方法;通过多元线性回归分析父母养育倦怠的影响因素。结果 两组在家庭功能评定量表各维度、简易应对方式量表(积极应对)、养育倦怠量表、孤独症行为量表、儿童孤独症评定量表、日常生活活动能力量表、儿童发育行为评估量表方面比较,差异有统计学意义(P <0.05)。Pearson相关分析结果显示,家庭功能、积极应对方式与父母养育倦怠之间存在显著的负相关(r=-0.186、-0.898,P=0.006、0.004),家庭功能与积极应对方式之间存在显著的正相关(r=0.048,P=0.005)。积极应对方式在家庭总体功能与养育倦怠中起部分中介作用,间接效应占总效应的37.98%。多元线性回归分析,家庭功能评定量表、简易应对方式量表、孤独症行为量表、儿童孤独症评定量表、日常生活活动能力量表、儿童发育行为评估量表评分是ASD患儿父母养育倦怠的影响因素(P <0.05)。结论 家庭功能和积极应对方式在ASD儿童父母养育倦怠中起重要作用。

育成期代谢能摄入量对蛋鸡生殖器官发育、激素水平和卵巢基因表达的影响

旨在研究育成期代谢能(ME)摄入量对蛋鸡生殖器官发育、激素水平和卵巢基因表达的影响。将720只6周龄海兰褐蛋鸡随机分为3组,每组6个重复,每个重复40只鸡。6~17周龄,各试验组饲粮粗蛋白质水平分别为17.5%(6~12周龄)和15.5%(12~17周龄),ME水平分别为12.34、11.11(12.34×90%)和9.87(12.34×80%)MJ·kg-1(分别为对照组亦即自由采食组、90%ME限饲组和80%ME限饲组),其他营养素水平相同。对照组试验鸡自由采食,其他试验组蛋鸡按照对照组蛋鸡采食量定量饲喂。试验期为6~17周龄。结果表明:1)随着育成期能量限饲强度增加,各试验组蛋鸡17周龄体重、体斜长和跖围均显著线性减少(P<0.001)。2)随着育成期能量限饲强度增加,血清尿素氮(UN)和葡萄糖(GLU)水平均显著线性减小(P=0.040,P=0.044),但血浆雌二醇水平显著线性增加(P=0.026)。3)对17周龄血液雌二醇水平差异最显著的自由采食组(ALF17W)和80%能量限饲组(ERF17W)蛋鸡卵巢基质部进行RNA-Seq分析,纯净序列匹配到鸡参考基因组的比例均超过了94.61%,Q20和Q30的纯净序列含量分别高于97.38%和92.87%,两组共筛选出1299个差异基因,ERF17W中961个下调,338个上调。GO功能富集分析发现,差异表达的mRNAs参与调节细胞增殖、发育和生殖等48个显著富集的GO条目,KEGG信号通路显著富集在25个显著富集的KEGG通路,其中cAMP信号通路、雌激素信号通路、类固醇激素生物合成和卵巢类固醇生成等是与能量代谢或生殖相关的通路。筛选到的cAMP反应元件结合蛋白(CREB)和类固醇生成急性调节蛋白(StAR)富集在cAMP信号通路,孕激素受体(PGR)、代谢型谷氨酸受体1(GRM 1)和细胞骨架蛋白角蛋白18(KRT 18)富集在雌激素信号通路。qRT-PCR结果显示10个随机选择的差异表达基因的表达趋势与RNA-Seq结果一致。综上可见,随育成期ME摄入量减少,育成期末蛋鸡体重、血清UN和GLU含量均显著线性减小,但血浆雌二醇水平显著线性增加,育成期ME摄入量可能通过调控卵巢组织StAR、CREB1、KRT18、PGR和GRM1等基因的表达,作用于cAMP信号通路和雌激素信号通路,以调控蛋鸡能量代谢和雌激素生成。

湖泊深水暂养过程中鳙鱼品质变化研究

为了研究天然水体长成鳙鱼在不同月份暂养过程中鳙鱼体形、肌肉营养、滋味、免疫及抗氧化物质的变化,采集花亭湖5月、8月、11月和次年3月暂养鳙鱼进行系统研究。结果显示,从体形来看,暂养处理对鳙鱼有瘦身效果;不同月份鳙鱼肌肉基本营养成分含量有差别,暂养处理后,鳙鱼肌肉蛋白质和脂肪含量降低,水分和灰分含量升高;脂肪酸组成发生变化,主要表现在饱和脂肪酸(SFA)含量降低,多不饱和脂肪酸(PUFA)含量升高;肌肉免疫和抗氧化成分含量随着暂养时间的延长显著降低;游离氨基酸总量随着暂养时间的延长不断提高,呈现甜味氨基酸占比不断提高;呈味核苷酸总量提高。

不同育苗方式对刺槐幼苗生长的影响

为了解不同育苗方式对刺槐幼苗生长的影响,以泰安市徂徕山林场种植的刺槐幼苗为研究对象,分别用播种育苗、扦插育苗和容器育苗3种方式进行育苗,并分析不同育苗方式对刺槐幼苗生长、根系形态和生物量产生的影响。结果表明:(1)扦插育苗方式下,刺槐幼苗苗高和地径明显高于播种育苗和容器育苗(P<0.05),且播种育苗苗高和地径高于容器育苗(P<0.05);(2)扦插育苗总根长、根表面积、根体积和根尖数显著高于播种育苗和容器育苗,播种育苗其次,容器育苗最低(P<0.05);(3)扦插育苗茎叶生物量、根系生物量、总生物量和根冠比均高于播种育苗和容器育苗,播种育苗高于容器育苗(P<0.05)。扦插育苗方式下,刺槐幼苗生长状况较为理想,可促进刺槐幼苗生长,改善其根部发育状态。

实验室饲养对中华蜜蜂雄蜂精液及转录水平基因表达的影响

为探索中华蜜蜂Apis cerana cerana Fabricius种用雄蜂的高效培育方法,本研究利用实验室和蜂群条件培育中华蜜蜂性成熟雄蜂,比较各实验组雄蜂的体重、可采集精液比例及精子活力,利用转录组测序技术解析实验室饲养对雄蜂基因表达的影响。结果表明,与蜂群饲养组相比,实验室饲养组中华蜜蜂性成熟雄蜂的精子活力无显著差异,但雄蜂的体重和可采集精液比例显著降低。转录组测序共筛选获得实验室饲养组雄蜂的差异表达基因602个,其中上调表达186个,下调表达416个。上调的差异表达基因显著富集于蛋白质结合、核质、淘汰的核质组分和胞内细胞器等19个GO功能分类;下调的差异表达基因显著富集于ATP合成耦合质子转运、线粒体内膜、呼吸体和碳水化合物代谢过程等22个GO功能分类,以及氧化磷酸化、碳代谢、脂肪酸降解和三羧酸循环等6条KEGG通路。表明实验室饲养可作为培育中华蜜蜂种用雄蜂的备选方法进行深入研究。实验室饲养可能通过抑制机体能量代谢和干扰线粒体功能影响雄蜂的生长和精子发生。研究结果为进一步研发中华蜜蜂种用雄蜂的工厂化培育技术提供了科学参考,有助于加速我国本土蜜蜂的良种选育进程。

基于Dynaform的汽车后风窗罩板成形工艺参数优化研究

文中以某汽车后风窗罩板为研究对象,解决其成形过程中的破裂和回弹缺陷。首先,运用Dynaform软件构建了符合实际工况的仿真模型;然后,选择对成形质量影响较大的模具间隙、摩擦因数、压边力和冲压速度作为主要因素,设计了4因素4水平的正交试验方案,并进行了仿真分析;接着,以最大减薄率和回弹作为评价指标进行综合评分,并采用Minitab软件对综合评分进行均值分析,获得了影响成形质量的各因素的主次关系和最优冲压工艺参数组合:摩擦因数为0.085,冲压速度为5000 mm/s,压边力为65 kN,模具间隙为1.15 mm;最后,选用上述工艺参数进行仿真分析和生产验证,产品拉延区域未出现破裂的成形缺陷,左右两端的弧形位置未见明显回弹。

鳡人工繁殖与苗种培育研究进展

鳡(Elopichthys bambusa)是大型凶猛肉食性鱼类,在大型水体生态系统中占据重要地位,也是我国重要的经济鱼类。近年来,由于种质退化、亲本数量锐减、养殖规模衰减、池塘规模化繁育技术不成熟等综合因素,导致其产业发展停滞甚至倒退,已无法满足市场需求。鳡亲本培育、亲本产后护理、规模化催产、驯食人工配合饲料、优良种质培育等领域仍然存在不成熟不完善之处,有较大的研究空间。建立完善的鳡繁育技术体系对推动鳡产业可持续、高质量发展至关重要。近20年来,鳡人工繁殖技术取得突破,苗种培育也取得了重要进展,特别是驯食人工配合饲料方面取得了重要突破,给鳡产业发展提供了关键保障。文章系统总结了鳡人工繁殖与苗种培育的研究进展,指出繁育环节中需要进一步研究和解决的问题,特别是亲本培育与产后护理、驯食及优良种质培育等方面需要进一步开展大量研究。文章进一步提出对应建议或对策,以期为鳡产业持续发展提供参考,也为其他大型肉食性鱼类产业发展提供了借鉴。

金定鸭不同养殖模式生产性能的比较分析

研究旨在比较分析金定鸭在笼养和地面平养饲养模式下的生产性能,为评价不同养殖模式下的蛋鸭生产性能提供参考依据。12周龄时,将600羽金定鸭分成2种模式饲养,其中300羽上笼饲养,其余300羽金定鸭为半开放式地面平养。饲养观察测定至72周龄。结果表明,笼养模式下金定鸭的开产日龄132.91 d、43周龄产蛋数149.26枚、72周龄产蛋数321.30枚、总蛋重23.74 kg,均分别优于地面平养模式的开产日龄139.63 d、43周龄产蛋数143.49枚、72周龄产蛋数308.63枚、总蛋重22.43kg;此外,蛋品质测定结果显示,笼养和地面平养的蛋品质没有显著差异。以上结果表明,金定鸭采用笼养模式较平养模式能获得更好的产蛋性能,适宜笼养。

汽车车身造型设计与气动力分析

为研究车身造型对气动力的影响,根据人机工程相关参数,运用Rhino软件的非统一有理B样条(non-uniform rational B-splines, NURBS)建模技术,构建车身外形,并采用计算流体动力学方法对其外流场进行仿真,得到气动力特性。流场中气流始终附着在车身表面没有出现分离,表明车身造型合理,有利于减小气动阻力。针对尾部结构进行曲线再造,改进后的模型的气动阻力明显减小;附加尾翼和鸭尾造型气动升力减小,侧倾力矩减弱,有利于提高汽车对地面的附着力,提高稳定性,更适合于赛车。文中采用的方法可为设计符合汽车空气动力学特性的车身造型方案及风洞试验提供理论参考。

烟叶日光大棚漂浮育苗气象条件分析

为掌握烟叶苗床期不同生育阶段对气象条件的需求,选取3个不同海拔高度的育苗日光大棚安装小气候站,结合棚外的烟叶生态气象站苗床期间的日照和总辐射量数据,对烟叶生育期叶龄生理指标进行观测,分析了不同海拔高度烟苗苗床期对温、湿、光的要求。结果表明:影响日光大棚内烟苗生长的生态环境因子表现为气温因子>水分因子>光照因子。育苗期间从播种到出苗需要14~19 d,每长1片真叶需要4 d左右;整个育苗期平均温度为12.0~15.5℃,相对湿度控制在72.4%,营养液平均温度为11.0~15.1℃,育苗期所需活动积温为555.1~640.8℃;日照时数为247.0~293.0 h,总辐射为550.5~686.7 MJ/m^(2)。本文对不同海拔高度烟叶幼苗苗床期对温、湿、光的要求进行了研究总结,为开展烟叶种植全生育期气象服务提供了理论支撑。

单针振动气力式辣椒精量排种器设计与试验

【目的】育苗移栽是辣椒种植普遍采用的方式,针对辣椒穴盘育苗播种环节存在的漏播现象,设计了一种用于漏播补种的单针振动气力式辣椒精量排种器,用于对穴盘中的空穴进行补种,从而提高生产效率。【方法】以“兴蔬皱辣2号”辣椒种子为研究对象,结合种子物理特性测定,对排种器振动供种机构、直线携种机构和控制系统进行分析和设计,并搭建了试验台。以种箱振动频率、气吸针真空度和气吸针直径为试验因素,以排种单粒率为试验评价指标,进行排种器单因素试验,确定种箱振动频率、气吸针真空度和气吸针直径具体取值范围分别为77~89 Hz、15~35 kPa和0.6~0.8 mm。在此基础上进行响应面试验,运用Design-Expert软件对试验数据进行方差分析、响应曲面分析和试验因素优化求解。【结果】确定了排种单粒率影响因素由大到小为气吸针真空度、气吸针直径和种箱振动频率,得出排种器最优作业参数为气吸针真空度27 kPa、气吸嘴直径0.7 mm、种箱振动频率85 Hz,样机试验排种单粒率为98.25%。【结论】该单针振动气力式辣椒精量排种器工作稳定,排种单粒率高,满足辣椒精量播种作业要求。

育龄夫妻三孩生育意愿分析及对策研究——基于福建龙岩的实地调查

为积极落实三孩生育政策,主动适应人口和计划生育工作转型发展的新要求,调研组基于龙岩市育龄夫妻三孩生育意愿的调查问卷数据及实地调研,得出结论:三孩生育意愿的影响因素主要表现在经济成本、制度保障和生育观念三个方面。为进一步优化生育政策,提高三孩生育政策及配套支持措施的针对性、可操作性,切实减轻群众生育、养育、教育负担,助力生育友好城市建设,建议加强顶层设计提供政策支持,着力提升系统保障功能,多管齐下降低家庭养育成本,营造良好的生育氛围。

大客车尾翼的数值模拟与风洞试验

为了研究尾翼对大客车气动特性的影响,采用数值模拟和风洞试验相结合的方法,从造型方案、位置布置、倾角变化等方面对大客车量产实车的3种尾翼进行研究。结果表明:布置在车身后围,与后围曲面过渡平顺,距后围距离恰当,倾角合适的尾翼能达到较好的减阻效果,可减小11.8%的气动阻力,产生一定节能效果,并具有后窗除尘的作用。