共查询到20条相似文献，搜索用时 78 毫秒
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运用包括非迭代三激发电子相关耦合簇CCSD(T)方法和Dunning等人使用的相关一致aug-CC-PVxZ(x=D,T,Q,5)自洽基组对XF(X=H,D,T)分子进行了结构优化,优化值然后被插值到CBS极限.结果表明随着x的增大aug-CC-PVxZ系列基组优化的结构逼近实验值,计算频率与实验值最大差距不足1%,最小仅为0.099%,平衡间距最大只有0.8%的差距.通过计算还表明:在结构优化和频率分析时CCSD(T)显示出优秀的特性,但在研究与边界态或解离有关的问题时,CCSD(T)不能给出良好的结果,相反CCSD方法却能给出合理的解离极限.最后我们研究了XF(X=H,D,T)的分子势能函数和光谱常数,理论结果与已知实验值吻合的非常好.首次获得了XF(X=H,D,T)系列分子的ωeye,ωeze,β,γ,He,Fe值. 相似文献
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YANGBo SUYah ZHOUBai-ling 《勤云标准版测试》2005,(2):150-154
A new closed-loop driving scheme for the silicon micromachined vibratory gyroscope (SMVG) is proposed. The push-pull driving is adopted and in-phase AC and reverse-phase DC voltages are applied in the driving electrodes placed in both sides of the active combs, respectively. Driving performance analyses show that the frequency spectrum between driving moments and noise signals is separated. Therefore, the model of the closed-loop control is set up with the phase lock loop (PLL). The requirements for phases and gains of the sinusoidal selfdrive-oscillation are met by PLL, thus the closed-loop circuit reaches the self-drive-oscillation. Phase conditions of the sinusoidal self-drive-oscillation and the characteristic of phase discrimination of the PLL are used to eliminate the coupling between driving and sense signals, and noise signals. Finally, experimental results show that the variations of both the driving frequency and the amplitude are all under 0.02%. The precision and the reliability of the gyroscope are greatly improved. 相似文献
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Mite （Varroa destructor） is one of the most serious parasite threats to the honey bee （Apis mellifera） reared in China. The beekeepers mainly use the drug to control and kill the mite in the past years, but the honey products may be contaminated and the mite is becoming drug-resistant. The main idea of this paper is to research the possibility of mite-resistant honeybee rearing by nutritional crossbreed. The larvae （Apis mellifera ligustica） are bred with the royal jelly of Apis carana carana, and then the morphological index of the worker generation, genotypic frequency and gene frequency of the MDH Ⅱ, genetic resemblance, and mite resistance are measured. The results show that： compared to the parent workers, the proboscis length, anterior wing area, the total length of the third and fourth dorsal plate of the abdomen, the length of the fourth dorsal plate of the tuberculum, the area of the sixth abdominal segment, and the area of wax mirrors are significantly different, but the differences in the brachium index, dactylus index, and wing claw are not significant. Moreover, there are some mutations in the genotypic frequency and gene frequency of the MDH Ⅱ. The mite resistance of the nutritional crossbreed worker is significantly higher. The morphological, physical, and biochemical characters, genetic resemblance, and the mite-resistant ability of the worker generation can be changed by nutritional crossbreeding. Nutritional crossbreeding can be a new way to breed the honeybee. 相似文献
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Sun Xiao-yang Wang Peng Xie Fu-chun Sun Hua-shan Guan Tong Zuo Yang Li Hong Chen Ya-jun 《东北农业大学学报(英文版)》2018,(3)
The mowing height and mowing frequency are the key factors that affect the turf quality and turfgrass growing ability. The purpose of this study was to reveal the alternative efficient interaction between mowing height and mowing frequency in Kentucky bluegrass turf management. The Kentucky bluegrass cultivar 'Kenblue'(Poa pratensis L.) was used to evaluate the interactions of mowing heights(H1, H4 and H7) and mowing frequencies(F2, F5 and F8) on the performance of turfgrass and turf physiological responses under the field condition. The results showed that the treatment of H7×F8 had perfect influence on the turf texture, root elongation, and also enhanced soluble sugar and free proline content in plants. While, the turf quality, color, uniformity and the increasing tiller numbers were performed more superior in the treatment of H4×F5 than other treatments. In all the interacting treatments, the relation between leaf green index and number of shoots(dm~2) was positively correlated, thus, it could be speculated that the proper mowing height with frequency had a strong impact on the increasing of turfgrass tillers. On the whole, the interaction of H4×F5 on turf quality was the most excellent treatment in this experiment. 相似文献
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《农业科学学报》2017,(2)
Area Sampling Frames(ASFs) are the basis of many statistical programs around the world. To improve the accuracy,objectivity and efficiency of crop survey estimates,an automated stratification method based on geospatial crop planting frequency and cultivation data is proposed. This paper investigates using 2008–2013 geospatial corn,soybean and wheat planting frequency data layers to create three corresponding single crop specific and one multi-crop specific South Dakota(SD) U.S. ASF stratifications. Corn,soybeans and wheat are three major crops in South Dakota. The crop specific ASF stratifications are developed based on crop frequency statistics derived at the primary sampling unit(PSU) level based on the Crop Frequency Data Layers. The SD corn,soybean and wheat mean planting frequency strata of the single crop stratifications are substratified by percent cultivation based on the 2013 Cultivation Layer. The three newly derived ASF stratifications provide more crop specific information when compared to the current National Agricultural Statistics Service(NASS) ASF based on percent cultivation alone. Further,a multi-crop stratification is developed based on the individual corn,soybean and wheat planting frequency data layers. It is observed that all four crop frequency based ASF stratifications consistently predict corn,soybean and wheat planting patterns well as verified by the 2014 Farm Service Agency(FSA) Common Land Unit(CLU) and 578 administrative data. This demonstrates that the new stratifications based on crop planting frequency and cultivation are crop type independent and applicable to all major crops. Further,these results indicate that the new crop specific ASF stratifications have great potential to improve ASF accuracy,efficiency and crop estimates. 相似文献
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CHAIYan-ju OUJi-kun RENChao 《勤云标准版测试》2005,(2):119-123
A new method is proposed for detecting and repairing cycle slips in GPS navigation based on the dual frequency observations. It can be implemented through the following three steps: (1) The integer ambiguities of the current epoch are substituted by that of the previous epoch, so the ambiguity parameters are removed from the observation equations. (2) The abnormal observations are detected using the quasi accurate detection (QUAD) method and the satellite pairs of these abnormal observations are determined. Then the coefficient matrix of these satellite pairs is recovered. (3) The cycle slips of these satellite pairs are calculated using the LAMBDA method and integer ambiguities of the current epoch can be determined by adding the cycle slips into the integer ambiguities of the previous epoch. The key of this method is that the abnormal observations must accurately he detected, i.e. , the satellites having cycle slips must correctly be judged. Finally, compared with other methods the feasibility of the method is verified. 相似文献
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Progenies derived from crosses between Solarium tuberosum and 2n pollen-Producing diploid hybrids, exhibit obvious hybrid vigor. The 2n pollen-producing clone can act as a bridge in crossing S. tuberosum and S. andigena with S. phureja. Populations from 4x-2x crosses show more unifomity and less segregation compared with that of 4x-4x crosses.
The parent-offspring correlation for the traits, starch content and tuber number, is significant at 0.01 level. The regrssion equations are Y (mp-F1)=1.0 1.2x and Y (mp - F1) = 5.3 0.8x, respectively. The 2n pollen-producing clones play an impotant role in increasing tuber stach content.
Estimates of the combining ability for the main yield components indicate that additive effect prodominatcs for such trais as plot yield, tuber weight per plant and starch content, whereas both additive and non-additive effects lay equal stress on mean tuber weight and non-additive effect is important for tuber number. In general, non-additive effect appears to be important in 相似文献
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HUXian-qi YUMin LINLi-fei WANGYang YUSheng-fu 《中国农业科学(英文版)》2004,3(8):598-603
Rice root nematodes, Hirschmanniella spp. parasitize in the roots of rice and water plant spread widely. Ten species of the genus Hirschmanniella Luc et Goody, 1964 (Nemata:Pratylenchidae) collected from the root of rice in Yunnan Province are reported. They are H. belli, H. caudacrena, H. diversa, H. gracilis, H. imamuri, H. mexicana, H. microtyla,H. mucronata, H. oryzae and H. spinicaudata, including seven species of important pathogenic nematodes of rice and two dominant species H. oryzae and H. imamari. Generally,the trend of species composition pattern is H. oryzae and H. imamari, which is a common composition pattern in the world, but the species composition mode varies with the difference of altitude and latitude. Their distribution relates to altitude and latitude closely, and also to the type of rice, such as indica or japonica rice. 相似文献
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分析了四夸克态的不同耦合道的色旋组态及不同耦合道的色旋组态之间的变换,进而采用拟合介子和重子质量得到的参数,在夸克间的色旋耦合相互作用下计算了X(3872)作为粲夸克偶素类四夸克态(cqcq--)(q=u,d)的质量,并在色旋机制下对X(3872)作为双夸克一双反夸克态和分子态进行了讨论.Abstract： Color-spin configurations and transformations between color-spin configurations in different coupled channels are analyzed. The mass of X(3872) is estimated in the color-spin force with the parameters obtained by fitting the masses of mesons and baryons. The X(3872) is discussed as a diquark-diquark bound state and as a molecular state. 相似文献
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本试验以菜豆品种先行者为试材,采用32孔、50孔两种规格穴盘,设置10、15、20、25 d等4个苗龄段,通过研究不同穴盘规格和苗龄对菜豆性状及产量的影响,筛选出适合菜豆育苗的穴盘规格和适宜的苗龄。结果表明：穴盘育苗的营养面积增大,菜豆产量随之增加,25 d苗龄条件下,32孔穴盘的前期产量和总产量均显著高于50孔穴盘;随着苗龄的增长,菜豆的前期产量和总产量呈增加趋势,其中25 d苗龄的产量显著高于其他苗龄。综合上述各项指标,菜豆育苗阶段,10 d苗龄可选用32孔、50孔穴盘,15 d以上秧苗选用32孔穴盘为宜。 相似文献
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氮素作为重要的营养元素,限制着小麦的生长发育和经济产量,筛选和培育耐低氮小麦品种是提高氮素利用率、降低生产成本的有效途径。以118份不同基因型小麦为材料,在低氮(0.1 mmol·L-1)和正常氮(5 mmol·L-1)条件下苗期水培,测定根干重、茎叶干重、根冠比、植株干重、最大根长、初生根数和二级初生根数等相关指标,采用模糊隶属函数法、主成分分析以及聚类分析法综合评价小麦品种的耐低氮性。结果表明,在低氮胁迫下小麦幼苗的根干重、根冠比和初生根数目显著提高,茎叶干重、植株干重和最大根长不同程度的降低,7个苗期性状指标在两个氮水平下均存在显著性差异。主成分分析提取3个主成分,贡献率分别为 43.575%、22.904%和17.873%,累积贡献率达 84.351%。以耐低氮性综合评价D值进行聚类分析,将118份小麦品种划分为强耐低氮型、耐低氮型、中间型、较敏感型和敏感型5类。筛选出3份耐低氮型小麦（齐大195、金丰7183和天民198）和2份强耐低氮型小麦（山农0917和鲁麦8号）。不同小麦品种的耐低氮机制不同,研究结果为小麦耐低氮品种的选育提供理论依据和材料基础。 相似文献
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ICP-OES法同时测定果蔬中铅、砷、镉、铬、铜、锡含量 总被引：2，自引：0，他引：2
果蔬样品经混酸消化后,控制一定的酸度,定容后应用等离子体发射光谱法(ICP-OES)对果蔬中铅、砷、镉、铬、铜、锡六种有害重金属进行测定,研究了分析测定条件,方法简单快速。测定结果表明,五种元素的加标平均回收率在91.0%~107%之间。其RSD均小于3.5%。按该方法进行处理及测定铅、砷、镉、铬、铜、锡,在选择的测定条件下最低检出限分别为0.0006 mg/kg、0.0003 mg/kg、0.00003 mg/kg、0.00005 mg/kg、0.00003 mg/kg、0.0006 mg/kg。 相似文献
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Segregation of form, color, movement, and depth: anatomy, physiology, and perception 总被引：63，自引：0，他引：63
Anatomical and physiological observations in monkeys indicate that the primate visual system consists of several separate and independent subdivisions that analyze different aspects of the same retinal image: cells in cortical visual areas 1 and 2 and higher visual areas are segregated into three interdigitating subdivisions that differ in their selectivity for color, stereopsis, movement, and orientation. The pathways selective for form and color seem to be derived mainly from the parvocellular geniculate subdivisions, the depth- and movement-selective components from the magnocellular. At lower levels, in the retina and in the geniculate, cells in these two subdivisions differ in their color selectivity, contrast sensitivity, temporal properties, and spatial resolution. These major differences in the properties of cells at lower levels in each of the subdivisions led to the prediction that different visual functions, such as color, depth, movement, and form perception, should exhibit corresponding differences. Human perceptual experiments are remarkably consistent with these predictions. Moreover, perceptual experiments can be designed to ask which subdivisions of the system are responsible for particular visual abilities, such as figure/ground discrimination or perception of depth from perspective or relative movement--functions that might be difficult to deduce from single-cell response properties. 相似文献
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通过野外调查、标本采集、分类学研究及资料考证,基本摸清了贵州樟科、莲叶桐科、景天科、堇菜科、柳叶菜科、鹿蹄草科、柿科、山矾科、木犀科等9个科药用植物资源的种类与地理分布.结果发现贵州现有樟科药用植物49种4变种,莲叶桐科药用植物5种,景天科药用植物21种,堇菜科药用植物19种1变种,柳叶菜科药用植物20种4变种,鹿蹄草科药用植物7种1变种,柿科药用植物9种1变种,山矾科药用植物12种,木犀科药用植物30种3变种.其中,4种为贵州特有药用植物,40种5变种为贵州药用新资源. 相似文献