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Microprecipitates in Semi-Insulating GaAs Single Crystals

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Rare Metals 1989年第1期9卷 23-27页

作者： Mo Peigen Zhu Jian Wu Ju Shanghai Institute of Metallurgy,academia sinica Acad sinica

The microprecipitates in the as-grown undoped and In-doped semi-insulating GaAs single crystals have been ex- amined by JEM 200 CX transmission electron *** microprecipitates consist of GaAs polycrystalline grains of 5～100nm in size have been evidenced in dislocated *** dispersive X-ray analysis shows that the mieropreeipitates are predominately arsenic-rich *** As/Ga atomic ratio of the microprecipitates in In-doped crystal is higher than that of undoped *** is suggested that the formation of the microprecipitates may be induced by the local fluctuation of compositional undercooling during crystal growth.

关键词： In GaAs Microprecipitates in Semi-Insulating GaAs Single Crystals

Neutron activation analysis (NAA) and geochemical studies of 38 elements in surface sediments from lower reach and estuary of Huanghe (Yellow) River

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Acta Oceanologica sinica 1990年第2期9卷 227-246页

作者： Li Peiquan Chih-An Huh Zhihxin Zhang Weizhi Tian Lu Guanshan

Using a neutron activation analysis technique, which involves gamma-spectrometry with a Ge(Li) detector coupled to a S40 multichannel analyzer and interfaced to a PDP-11 computer, we determined thirty-eight elements in sediments from the lower reach (downstream from Jinan) and estuary of Huanghe. The results are discussed in this *** inter-elemental correlations, it ts found that a large number of metals (***, Co, ***, Rb, Sc, Ti, Ta, V and Zn) correlate positively with Fe. Ba and Ca correlate positively with Al. Whereas some elements (e. g. , Ti and lanthanides) show no correlation with either Fe or Al. On the other hand, Hf and Zr show a negative correlation with Fe. Elements which tend to be scavenged by Fe and Al colloids or suspended particles are enriched in sediments at the Huanghe Estuary relative to its lower reach. On the other hand, the contents of some elements (e. g. , Zr,Hf,U, Ba, etc. )are higher in sediments from the lower reach of Huanghe than in the estuarine sediments,which may be related to the sorting during deposition of source materials. On the basis of their chemical property and geochemical behavior, the 38 elements we studied are classified into seven groups. (1) weathering-prone elements,group A:K,Rb, Cs and Na; (2) weathering-prone elements, group B:Mg, Ca, Ba and Al; (3) transition elements:Fe, ***, Zn, As, Sb, Mn, Cr, W,Mo,V, Ta and Sc; (4) rare elements:group A (Zr and Hf) and group B (Ti); (5) rare earth elements:the lanthanides; (6) halogens: Cl and Br; amd (7) natural radioactive elements:U and Th. The basis for this classification is discussed and we emphasize that geochemical associations of elements in the natural environment are not necessarily in accord with their chemical properties as dictated by position at the periodic table.

关键词： Yellow and geochemical studies of 38 elements in surface sediments from lower reach and estuary of Huanghe River NAA

STUDY OF PHASES IN U-10wt%Zr ALLOY BY NEUTRON DIFFRACTION

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Acta Metallurgica sinica(English Letters) 1995年第3期8卷 174-180页

作者： XIE Guoqiang YANG Jijian ZHANG Baisheng LI Wendan(China Institute of atomic energy, Beijing) China Inst of atomic energy Beijing China

U 10wt%Zr alloy has been analysed by neutron diffraction method to determine the constituent phases and their crystal *** collected diffraction data are processed using Rietveld' s profile technique (with program“ Fullprof ”). Four phases,α-U,δ, γand α Zr, in the alloy at room temperature and the corresponding volume fractions as well their structural parameters are obtained from the data analysis, For the δ-phase, a partially ordered unusual hexagonal structure of the modified C32(AlB2) type is confirmed.

关键词： U-10wt%Zr alloy neutron diffraction δ-phase

FROM UNWEIGHTED TO WEIGHTED GENERALIZED FAREY ORGANIZED TREE AND THE PYRAMID NETWORKS

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Journal of Systems Science & Complexity 2010年第4期23卷 681-700页

作者： Yong LI·Jinqing FANG·Qiang LIU China Institute of atomic energy,Beijing 102413,China. China Institute of atomic energy Beijing China

Generalized Farey tree network(GFTN)and generalized Farey organized pyramid network(GFOPN)model are proposed,and their topological characteristics are studied by both theoreticalanalysis and numerical simulations,which are in good accordance with each *** weightedGFTN is studied using cumulative distributions of its Farey number value,edge weight,and *** results maybe helpful for future theoretical develonment of hvbrid models.

关键词：金字塔网络广义加权组织 Farey树数值模拟动力模型

MULTIGROUP THEORY FOR NEUTRON TRANSPORT

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Science in China,Ser.A 1979年第10期 1114-1127页

作者：阳名珠朱广田 Institute of atomic energy academia sinica Institute of Mathematics academia sinica

Using the method of functional analysis, we have established a rigorous mathematical treatment of multigroup approximation for neutron transport. It is proved that in L~p (1≤penergy) variable is not discretized], that the eigenvalues spectrum of the exact transport operator can be approximated by the eigenvalues spectrum of multigroup transport operator, and that the nonnegative eigenfunction of the multigroup transport operator converges to the corresponding nonnegative eigenfunction of the exact transport operator. The order of the magnitude of the rates of convergence is also indicated.

关键词： MULTIGROUP THEORY FOR NEUTRON TRANSPORT lim 一甲口声

Effects of Y211 phase contents on the critical current density J_c and microstructural analysis in YBCO bulk superconductors

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Rare Metals 2002年第4期21卷 282-288页

作者： SHA Jianjun, YU Gang, and YU JinnanChina Institute of atomic energy, P. O. Box 275-51, Beijing 102413, China China Institute of atomic energy P.O. Box 275-51 北京 102413

YBCO bulk superconductors were prepared by the solid state reaction andtop-seed-melt-textured growth (TSMTG) process. By using the AC susceptibility measurement, thecritical transition temperature T_c of samples is 91.5 K for the highest value, and the transitionwidth ΔT_c is less than 1 K. The highest magnetization critical current densities J_c achieved 10~6A/cm^2 under 5 T at 10 K and 1.35X10^4 A/cm^2 under 2 T at 70 K (H//c), respectively. The resultscombining the SEM observation indicate that doping of Y211 particles is more effective in improvingthe growth quality of melt-textured YBCO superconductor and in reducing the micro-cracks ofspecimens. Doping of Y_2O_3 powder forms the rod-shaped Y211 particles, but doping of Y211 particlesdirectly to matrix materials forms the spherical Y211 particles mainly. Combining themicrostructures with J_c measurements shows that the interfaces are most important on flux bundlepinning, in which the gradient of free energy is larger than that of other place between the Y211particles and the Y123 matrix materials.

关键词： quasi-single domain melt-textured Y211 particles critical current density magnetic flux pinning

analysis of umayyad islamic silver coins (Dirhams) by using instrumental neutron activation analysis

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Nuclear Science and Techniques 1999年第1期10卷 61-64页

作者： Bakraji E H Sarhell A (atomic energy Commission of Syria, Damascus-Syria) atomic energy Cornmission of Syria 叙利亚

Islamic silver coins (Dirhams) running the period between 107 to 126 Hijri( (726-743 AD), which belong to the Umayyad Empire period, 41-132 hijri (661-750 AD), were selected for analysis by using instrumental neutron activation analysis techniques. During this period (105-126H), (724-743AD), the Caliph Hisham Eben Abdlemalek ruled the Umayyad Empire. Dirhams were irradiated in a reactor neutron activation facility. Levels of various elements viz. Cu, Ag and Au were estimated. It was found that the average silver concentration, the base constituent of the Dirham, was about 88 wt%. Correlation between the composition of Dirhams and the historical implications was discussed.

关键词：考古学中子激活分析伊斯银第

DETERMINATION OF MICROELEMENT IN THE HAIRS OF SILICOSIS BY NEUTRON ACTIVATION analysis

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Chinese Science Bulletin 1989年第22期34卷 1934-1935页

作者：洪长福张朝和屈桂茹 Zhejiang Academy of Medicine Hangzhou 310013PRC Institute of atomic energy Academia SinicaBeijing

The effect of microelement on health is a new subject ongoing since the seventies. Some diseases may be related to changes of some elements. Since the last few years changes of Cu, Zn and other elements in the serum a... 详细信息

关键词： ongoing glutathione peroxide

Investigation on the eigenvalue-equation problem of molecular crystals and polymers

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Chinese Journal of Chemistry 1990年第6期8卷 481-491页

作者： YAN, Ji-Min ZHANG, Qi-Yuan, Institute of Chemistry, academia sinica, Beijing 100080 Institute of Chemistry Academia Sinica Beijing 100080

One-dimensional periodic system, such as molecular crystal and polymer, can be expressed as ... ABABAB ... structure, where A and B stand for a complete molecule or a part of a molecule. When (AB) is taken as a structure unit, one can obtain the complex generalized eigenvalue-equation H^(AB) (k) C^(AB) (k)=S^(AB) (k)C^(AB) (k)E^(AB) (k); and if (BA)is taken as a structure unit, the corresponding eigenvalue-equation is H^(BA)(k) C^(BA)(k)=S^(BA)(k) C^(BA)(k) E^(BA)(k). The relationship between the two equations has been investigated. The results of theoretical analysis are E_m^(BA) (k)= E_m^(AB)(k); C_(j_am)^(BA)(k)=C_(j_am)^(AB). exp (i△) and C_(j_bm)^(BA)(k)=C_(j_bm)^(AB)(k). exp[i(k.R_(-1)+△)]=C_(j_bm)^(AB)(k)× exp (i△??) where j_a and j_b are the index number of atomic orbitals within (A) and (B) respectively, and m stands for the index number of crystal or polymer orbitals. This result has been verified by the concrete calculation of three periodic systems: (1) hydrogen-molecular chain, ...H (A) H (B) ... H (A) H (B) ..., (2) polyphenylene, ... (A) (B) (A) (B) ..., where (A) and (B) stand for =C (CH=): and (=HC)_2 C= respectively, and (3) the TCNQ molecular column, ... TCNQ (A). TCNQ (B) ... TCNQ (A). TCNQ(B)... . The results can be generalized to two- and three-dimensional systems straightforwardly.

关键词： BA exp AB