Effect Correction of the Cavity Geometry of a Resonant Silencer on the Resonance Frequency

A new connector end correction is presented on the basis of the three dimensional finite element results, which is for the lumped-parameter formula used to predict the resonance frequency of a silencer having various depths to width ratio of the cavity. The problems of the low accuracy are solved even no use for some cavity dimensions of the lumped-parameter formula.     

Influence of Units and Assemble on DC Flashover Voltage of Iced Insulator Strings at High Altitude Districts

Based on artificial tests of iced DC XZP-210 insulator strings carried out in the artificial climate chamber, the authors analyze the effects of units and assemble on the DC flashover voltage of iced insulator strings at high altitude districts. The test results show that the relationship between the DC icing flashover voltage and the insulator units is seemly linear with the increase of altitude or pollution level, although the linear relation is not obvious at the low altitude or pollution level. There is influence of the assembled form on icing flashover voltages, the flashover voltage of the horizontal string of iced insulators is highest while that of the vertical string is lowest. For various assembled forms, the effects of the air pressure on the flashover voltage of the horizontal string are most obvious.     

An Approach of Pulse Waveform Integral to Modeling Resonant Converters

A novel approach to modelin8 resonant conventers, was presented in this paper.The variant subtopologies of a converfer are unified into an equiualent topology by the periodicpulse functions;Laplace transforms of the sampled function ,insteady of continuous ,of a small sig-nal variable are made;furthermore,the linear approximation is processed according to the differenttypes of converters, The conventional series and parallel converters are used as examples to discussthe principles of the approach. Finally the computer calcultion data is compared with the experiment results to con firm the models to be correct.     

Analysis and Countermeasures of the Power Noise During High Frequency PCB Design

The paper analyses many forms of power supply noise interference in the high frequency PCB and the relevant reasons. Combining several formulas with the relevant engineering experience, the authors bring forward a lot of related means; finally conclude the chief principle that controlling power noise should abide by.     

基于5.8SrDNA/ITS序列的几种内蒙古棘豆属植物分子系统学研究

提取小花棘豆(Oxytropis.glabra DC.)、小叶小花棘豆(O.glabra var.tenuis)、刺叶柄棘豆(O.aciphylla Ledeb.)、砂珍棘豆(O.racemusa Turcz.)、多叶棘豆(O.verticillaris (L.)J.N)、黄毛棘豆(O.ochrantha Turcz.)基因组DNA,扩增其5.8SrDNA/ITS序列并测序,将所测序列与GenBank中疏毛棘豆(O.pilosa)和长白棘豆(O.anertii)5.8SrDNA/ITS序列进行同源性比对,利用MEGA4.0软件采用Neighbor-joining法构建系统发育树,旨在为棘豆属下种间及种下分类研究提供分子依据.结果表明:多叶棘豆、砂珍棘豆和黄毛棘豆构成姐妹群,并在部分地理种群上混杂,认为将三者归入真棘豆亚属Subgen.Euoxytropis轮叶棘豆组Sect.Baicalia Stell.ex Bunge更合理.小叶小花棘豆与小花棘豆亲缘关系很近,支持将其视为变种的观点.刺叶柄棘豆的不同地理种群形成两大分支,对其在亚属水平上的分类还需进一步商榷.研究赞同棘豆属植物为单系起源,认为种内不同地理种群间的亲缘关系在一定程度上受到了植被类型和生境的影响.     

Behavior of Loose Sand-structure Interface Undergoing High Frequency Cycle Shearing

The behavior of loose sand-structure interface under the high frequency cycle shearing is analyzed by using Particle Discrete Element Method (DEM).The changes of sand box porosities of DEM model and sand volume strains are examined in detail.The results show that sand volumetric shrinkage due to shearing is not obvious in spite of the larger loose sand particle friction coefficients and particle stiffness.The particle stiffness ratio has a little effect on the mechanical properties of sands.In addition,the decrease in volume of sand under shearing is more obvious with the increase of the confining pressures.Moreover,the decrease in volume of loose sand under shearing is greater with the increase of the high frequency cycle shear amplitude and the shear frequency.     

The Mechanism and Kinetics of Parathion Degradation under High Frequency Ultrasonic Irradiation

The mechanism and kinetics of parathion degradation was investigated under high frequency ultrasonic irradiation in aqueous solution. The pseudo first order kinetic model and the response surface methodology (RSM) were proposed to evaluate the effect of ultrasonic frequency, power and initial concentration on sonochemical degradation of parathion. With the response surface experiments and quadratic fitting model, it was clearly indicated that the quadratic model was significant (P=0.000 2) and the lace of fit was not significant (P=0.113 6). The R2 of the model was 0.973 3. Ultrasonic power, initial concentration and the square of ultrasonic frequency were significant items for the model. And it was also indicated that there was an optimal frequency for parathion degradation with the operating conditions and the degradation rate of parathion was found to decrease with increase of initial concentration and decrease of power.     

高压交直流同塔输电线路无线电干扰与可听噪声的计算

为了寻求一种适合交直流同塔架设线路的无线电干扰与可听噪声计算方法,从理论上分析了混合线路表面场强的特点,利用线性叠加原理求出混合线路表面场强,并结合晴天和雨天对交流和直流线路电晕程度的不同影响,提出在同一种天气状况下计算交直流线路无线电干扰与可听噪声。用3种计算无线电干扰与可听噪声的方法,分晴天和雨天情况进行计算比较,结果表明3种方法中BPA修正公式计算值最大,该方法可视为目前计算交直流同塔线路无线电干扰与可听噪声的有效方法。     

茅苍术试管苗继代培养的ISSR及MSAP分析

为探究茅苍术试管苗在长期继代培养中的遗传稳定性与DNA甲基化变化,保证工厂化生产种苗品质.以茅苍术幼嫩顶芽为初始材料,建立高效离体快繁体系进行长期继代培养,并运用ISSR、MSAP分子标记技术对不同继代次数的试管苗进行分析试验.结果 显示不同继代次数的10个样本遗传多样性较低,具有遗传稳定性较高.其中,第1代与第10代...     

拟南芥PUB10和PUB11基因抵抗丁香假单胞杆菌番茄致病变种DC3000株的功能分析

丁香假单胞杆菌Pseudomonas syringae pv tomato(Pst)DC3000是研究植物免疫机制的常用病原菌。为分析拟南芥E3泛素连接酶PUB10、PUB11在免疫中的功能,本研究构建了pub10/pub11双突变体。在分析拟南芥PUB10、PUB11序列相似性和进化关系的基础上,比较了pub10/pub11双突变体和Col-0对Pst DC3000的敏感性、MAPK磷酸化水平、ROS产生的影响,并检测JA信号响应途径和免疫防御相关的部分代表性基因的表达量。结果表明PUB10、PUB11氨基酸序列高度保守,pub10/pub11双突变体对Pst DC3000的侵染更敏感,侵染后叶片病原菌数目明显增多,MAPK磷酸化水平迅速下降,ROS释放量降低,JA信号响应基因(LOX3,JR2)、免疫防御负调控基因(NIMIN1,WRKY38,WRKY62,RIN4)表达量上升显著高于Col-0,而免疫防御正调控基因(AZI1,EDS1,PAD4,EDS5,FMO1,NPR1)表达量显著低于Col-0。由此推断,AtPUB10、AtPUB11在防御Pst DC3000中起正调控作用,并且存在功能冗余。研究结果为进一步探索PUB10、PUB11调控植物防御的分子作用机制和分子育种提供了依据。     

作物超高产栽培与株型育种的光合作用基础——-以水稻为例

粮食安全问题是中国乃至世界未来面临的重要问题。提高作物的光合作用对解决粮食安全保障具有重要意义。作物叶片利用光能的能力受外界环境的影响,同时群体对小环境的影响反过来又影响叶片的光合作用。本文以水稻为例从栽培和株型育种两个方面讨论了优化群体结构、实现作物超高产的途径。     

牡丹组化学成分及药理作用研究进展

牡丹组植物的化学成分为单萜类、酚类化合物、茋类、三萜类、黄酮类等。其药理作用主要表现在对心血管系统的作用,以及抗癌、抗炎、镇痛、抗真菌、抗病毒、抗糖尿病等。     

北宁市葡萄鲜贮基地发展现状

对辽宁省北宁市鲜食葡萄基地建设、贮藏保鲜产业与技术发展的历史与现状、采取的措施进行了分析总结,为我国鲜食葡萄产业的发展提供理论借鉴。     

不同杀菌剂对甘薯茎基部腐烂病的防控试验

为有效防控甘薯茎基部腐烂病害,在2016 年田间试验的基础上,2017 年选用5 种杀菌剂的不同浓度或其中2 种杀菌剂混用对甘薯茎基部腐烂病进行田间防控试验。结果表明,以50%多菌灵100 倍液于扦插前浸薯苗、扦插后在薯苗基部浇施,在5 月中旬—6 月上旬扦插甘薯苗的条件下,大约7 月上中旬甘薯茎基部腐烂病未发病至初发病时,在甘薯茎基部每隔10 天左右,连续喷施防治3 次的防效最好,达60.10%,产量达18798.61 kg/hm2,比对照增产389.51%,且极显著地高于其他处理。     

Climb Height and Overflow of Grout in Shaft Base Grouting

Based on the assumptions of exponential fluid and narrow plate model, formulas for calculating the climb height of grout in shaft base post grouting was deduced. It is shown that the climb height of grout is mainly related to the grouting pressure, the shaft length, the shaft diameter and the mudcake thickness. With the theoretic analysis and case study, it is indicated that thicker mudcake, higher grouting pressure and shorter shaft length would lead to larger climb height and larger risk of overflow. The overflow of grout would be prevented by reducing the grouting pressure, the mudcake thickness and debris thickness. The overflow of grout can also be prevented by increasing the strength of mudcake. For the overflow shafts, intermission grouting would be employed. Compared with the ordinary shafts, the former has higher bearing capacity than the latter, resulting from the grout upwards along the shaft soil interface.     

北京密云某养殖场雷电灾害事故分析与对策

雷电灾害事故分析有助于更好地掌握雷击途径和方式,认识雷电致灾规律,从而采取更有效的防护措施。针对2014年7月1日北京市密云县西田各庄镇某养殖场发生的雷电灾害事故,统计分析雷击时间段内该区域闪电定位资料;根据滚球法判断养殖场是否在直击雷保护范围内,计算牲畜位置处跨步电压和养殖棚雷电静电感应电压。通过逐项计算和分析,结果表明：牲畜遭旁侧闪络和接触电压致死。雷电的静电感应在金属棚上产生高电压,由于金属棚的支撑钢架结构未做接地,感应电荷释放通道不顺畅,与地面存在电位差,发生旁侧闪络,以及当牲畜接触到钢结构后,高电位通过牲畜向地面释放,致使牲畜死亡。最后提出了对应的防护措施和方法,减少或避免以后类似雷电灾害事故的发生。     

江门林业高新技术示范区总体规划概略

江门林业高新技术示范区项目建设目的在于促进林业科技成果转化,推进林业生态建设,促进江门社会经济可持续发展。通过采取政府支持与市场化运作相结合、林业与旅游相衔接、与省内科研机构分工合作等建设方法,江门林业高新技术示范区将成为集生态林业研究、开发、推广、服务于一体,并融合林业科普、生态教育、旅游于其中的“生态型林业高科技产业园”。     

食品生物技术小规模实训基地建设与运行研究

食品生物技术小规模实训基地是食品生物技术专业学生的校内实训场所,在实现人才培养目标中起着重要作用。综述了四川工商职业技术学院食品生物技术小规模实训基地建设与应用的现状、存在问题和解决途径。     

白菜型油菜DFR基因的克隆与序列分析

By using RACE (rapid amplification ofcDNA ends) based homologous cloning strategy, we have successfully isolated the genomic and full-length cDNA sequences of a gene encoding typical DFR (dihydroflavonol-4-reductase) from black-seeded Brassica campestris L. var. oleifera DC.. The gene, designated BcDFR here, is 1 722bp in length and harbors 5 introns with typical splice sites of plant DFR genes. BcDFR cDNA is 1311bp in length with a 1 158bp ORF as well as a 25bp 5‘ UTR and a 128bp 3‘ UTR. The encoded BcDFR protein is 385 aa with a calculated Mw of 42.85kD and a pI value of 5.55. The nucleotide and amino acid sequences of this gene share extensive homologies to plant DFR genes of wide origins especially high similarities to Cruciferous DFR genes. Sequence analyses such as phylogenetic analysis, conserved domain search and substrate specificity region detection all indicated that BcDFR gene is a quite potentially biofunctional gene. Its cloning enables us to further dissect the possible relatedness between DFR gene and Brassica seed coat color traits and to create transgenic novel yellow-seeded rapeseed germplasm through antisense- or RNAi-suppression of DFR gene expression in black-seeded elite cultivars.     

超高茬麦套稻的产量及低碳效应分析

通过对超高茬麦田套稻稻作方式的机理进行了介绍,分析了其低碳优势和高产原因,为现代农业生产提供参考。