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101.
LetA={a
1, …,a
k} and {b
1, …,b
k} be two subsets of an abelian groupG, k≤|G|. Snevily conjectured that, when |G| is odd, there is a numbering of the elements ofB such thata
i+b
i,1≤i≤k are pairwise distinct. By using a polynomial method, Alon affirmed this conjecture for |G| prime, even whenA is a sequence ofk<|G| elements. With a new application of the polynomial method, Dasgupta, Károlyi, Serra and Szegedy extended Alon’s result to
the groupsZ
p
r
andZ
p
rin the casek<p and verified Snevily’s conjecture for every cyclic group. In this paper, by employing group rings as a tool, we prove that
Alon’s result is true for any finite abelianp-group withk<√2p, and verify Snevily’s conjecture for every abelian group of odd order in the casek<√p, wherep is the smallest prime divisor of |G|.
This work has been supported partly by NSFC grant number 19971058 and 10271080. 相似文献
102.
103.
采用深度刻蚀与XPS能谱研究缓蚀膜/镀铜层/铁基体界面成分 总被引:4,自引:2,他引:2
为了探索焦磷酸盐镀铜层与铁基体结合强度差的原因,采用波谱技术,分析了纵向界面各种元素的成分变化,讨论了金属基体表面粗糙度对元素分布的影响.根据刻蚀时间可将膜层分为三部分:N,O量迅速减少的表面层,有基本固定组成的中间层和占一半厚度的出现基体元素的混合干扰层.通过对后期混合层中氧含量的分析,可得出镀铜层/铁基体界面含氧层的存在是影响电镀层与基体结合强度的主要原因的结论. 相似文献
104.
SUPERCONVERGENTAPPROXIMATIONSFORWIENER-HOPFEQUATIONS¥SHIJUN(石军)(DepartmentofBasicScience,PetrolieumUniversity,Beijing102200,C... 相似文献
105.
This paper investigated the reinforcing effects of a hybrid filler, including talc and exfoliated graphene nanoplatelets (xGnPs), in polypropylene (PP) composites. In order to increase the interphase adhesion, maleic anhydride grafted polypropylene (MAPP) was added as a compatibilizing agent to the PP/talc/xGnP composites. The experiments were designed according to response surface methodology (RSM) to optimize the effects of three variable parameters, namely talc, MAPP and xGnP, on the mechanical properties. In the sample preparation, three levels of filler loading were used for talc (0, 15, 30 wt%), xGnP (0, 0.75, 1.5 wt%) and MAPP (0, 2, 4 wt%). From the analysis of variance (ANOVA), it was found that the talc and xGnP play a significant role in the mechanical properties and morphology of the composites, as proven by scanning electron microscopy (SEM) and differential scanning calorimeter (DSC). In order to simultaneously maximize these mechanical properties, the desirable values of the additives were predicted to be 30 wt% for talc, 4 wt% for MAPP and 0.69 wt% for xGnP. The obtained normal probability plots indicated good agreement between the experimental results and those predicted by the RSM models. 相似文献
106.
Conductivities were measured for the ternary systems NaCl-LaCl(3)-H(2)O and KCl-CdCl(2)-H(2)O and their binary subsystems NaCl-H(2)O, KCl-H(2)O, CdCl(2)-H(2)O, and LaCl(3)-H(2)O at 298.15 K. The semi-ideal solution theory for thermodynamic properties of aqueous solutions of electrolyte mixtures was used together with the Eyring absolute rate theory to study conductivity of mixed electrolyte solutions. A novel simple equation for prediction of the conductivity of mixed electrolyte solutions in terms of the data of their binary solutions was established. The measured conductivities and those reported in literature were used to test the newly established equation and the generalized Young's rule for conductivity of mixed electrolyte solutions. The comparison results show that the deviation of a ternary solution from the new conductivity equation is closely related to its isopiestic behavior and that the deviations are often within experimental uncertainty if the examined system obeys the linear isopiestic relation. While larger deviations are found in the system with large ion pairing effect, the predictions can be considerably improved by using the parameters calculated from its isopiestic results. These results imply that the previous formulation of the thermodynamic properties of aqueous solutions of electrolyte mixtures has a counterpart for transport properties. 相似文献
107.
Investigation of scale inhibition mechanisms based on the effect of scale inhibitor on calcium carbonate crystal forms 总被引:1,自引:0,他引:1
Zhang GuiCai Ge JiJiang Sun MingQin Pan BinLin Mao Tao Song ZhaoZheng 《中国科学B辑(英文版)》2007,50(1):114-120
To probe the scale inhibition mechanisms,calcium carbonate scale occurring before and after the ad- dition of scale inhibitors was collected.The results from scale SEM confirm that,without scale inhibitor, calcium carbonate scale shows rhombohedron and hexagon,which are the characteristic feathers of calcite.After addition of inhibitors,morphology of scale is changed,and the more efficient the scale inhibitor is,the more greatly the morphology is modified.To elucidate the scale constitute,they were further analyzed by FT-IR,XRD.Besides calcite,vaterite and aragonite occur in calcium carbonate scale after addition of inhibitors,and the higher scale inhibition efficiency is,the more vaterite presents in scale.It can be concluded that the alteration of morphology is ascribed to the change of crystal form. There are three stages in the crystallizing process including occurrence and disappearing of unstable phase,occurrence and disappearing of metastable phase,development of stable phase.Without scale inhibitors,metastable phases usually transform into stable phase,thus the main constitute of formed scale is calcite.When scale inhibitors are added,both formation and transformation of metastable phases are inhibited,which results in the occurrence of aragonite and vaterite.From the fact that more vaterite presents in scale with a more efficient scale inhibitor added,we can see that the function of scale inhibitor is realized mainly by controlling the crystallizing process at the second stage. 相似文献
108.
Jian-Bo Qu Xing-Zhong Wan Yan-Qin Zhai Wei-Qing Zhou Zhi-Guo Su Guang-Hui Ma 《Journal of chromatography. A》2009,1216(37):6511-6516
Using agarose coated gigaporous polystyrene microspheres as a base support, a novel anion exchanger (DEAE-AP) has been developed after functionalization with diethylaminoethyl chloride. The gigaporous structure, static adsorption behavior, and chromatographic properties of DEAE-AP medium were characterized and compared with those of commercially available resin DEAE Sepharose Fast Flow (DEAE-FF). The results implied that there existed some through pores in DEAE-AP microspheres, which effectively reduced resistance to stagnant mobile phase mass transfer by inducing convective flow of mobile phase in the gigapores of medium. As a consequence, the column packed with DEAE-AP exhibited low column backpressure, high column efficiency, high dynamic binding capacity and high protein resolution at high flow velocity up to 2600 cm/h. In conclusion, all the results suggested that the gigaporous absorbent is promising for high-speed protein chromatography. 相似文献
109.
采用高温固相反应法合成了锂离子电池正极材料LiCoO2, 用粉末X射线衍射(XRD)和扫描电子显微镜(SEM)等技术对材料的形貌与结构进行分析. 平面反射和透射X射线粉末衍射数据表明, 目前商品LiCoO2样品XRD图谱的(104)和(003)衍射峰强度比(I(104)/I(003))主要反映了LiCoO2晶体c轴方向的择优取向, 而不是Li、Co原子的占位有序程度. I(104)/I(003)比值越小, 晶体择优取向度越高. 晶体无择优取向LiCoO2粉末材料的衍射峰强度比I(104)/I(003) 应为95%左右. 因此, 不能用I(104)/I(003) 的比值大小作为实际LiCoO2材料晶体内Li、Co 原子排列是否有序的主要证据. 澄清了长期有争议的关于锂离子二次电池正极材料LiCoO2的X射线衍射峰强度比问题. 相似文献
110.