Adiabatic potentials of linear three-site mixed-valence systems

We propose a method for calculating adiabatic potentials of linear or quasi-linear threesite systems of mixed valence. The method is based on transformation of the potential energy matrix to two effective interacting modes. The adiabatic potential is calculated and its extrema are found. The electronic wave functions at the minima of the adiabatic potential correspond to complex charge distributions in a cluster. The barrier to transition of the extra electron between the terminal atoms is lower than for the transition from the terminal atom to the central atom.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 129–134, March–April, 1989.     

System for the formation of an electron beam in a 258 GHz gyrotron designed for experiments on dynamic polarization of nuclei

We consider the features of a system for the formation of an electron beam in a continuouswave high-stability gyrotron at the second gyrofrequency harmonic with an operating frequency of 258 GHz. The problems related to the maintenance of the required beam parameters are analyzed. The procedure and results of numerical simulation of the electron gun and collector of the gyrotron are described. The influence of various physical factors on the characteristics of the electronoptical system of the gyrotron are studied. The design of the electron beam formation system is described along with the results of measuring its parameters.     

需求可变性降低对均值CVaR约束销售努力决策库存系统的影响

本文运用Levy提出的变换研究需求可变性降低对风险偏好零售商的库存决策、销售努力决策和期望效用的影响,用均值CVaR刻画零售商的风险偏好特性,它包括风险厌恶、风险追求,也具有损失规避的特性。首先,运用该变换定量刻画需求可变性的降低,证明该变换蕴含经典随机占优中的割准则序和二阶随机占优等。其次,给出系统的最优订货量、最优期望效用和最优销售努力水平,得到它们关于风险偏好系数的单调性,并给出降低需求可变性对期望效用的影响。第三,针对风险中性、风险厌恶(最大化CVaR)和风险追求(最小化CVaR)这三种特殊情况得到相应的结果,并给出企业在库存决策和促销决策的管理启示。最后,通过数值例子验证了得到的研究结果并给出相应的管理启示。     

Dielectron measurements during heavy ion collisions at \sqrt {s_{NN} } = 200 GeV in the PHENIX experiment at RIHC

The production of dielectron pairs is measured in PHENIX experiment during p + p, d + Au, Cu + Cu, and Au + Au collisions at $\sqrt {s_{NN} }$ = 200 GeV. In the mass region between φ and J/ψ mesons, the yield is consistent with expectations from correlated production. In the mass region below φ mesons, the p + p and d+ Au spectra are well described by known contributions from light meson decays. In contrast, the Au + Au minimum bias spectrum in this region is enhanced by a factor of 4.7, concentrated at low p _T < 1.5 GeV/s and rapidly rising with centrality. Existing theoretical models cannot describe the observed enhancement.     

不同助剂对CuO-ZnO/SBA-15催化CO_2加氢制甲醇性能影响的研究

以硅质骨架结构介孔分子筛SBA-15为载体,采用浸渍法合成CuO-ZnO/SBA-15(CZ/SBA-15)、CuO-ZnO-MnO_2/SBA-15(CZM/SBA-15)、CuO-ZnO-ZrO_2/SBA-15(CZZ/SBA-15)三组多孔催化剂,在固定床反应器上评价了各组催化剂催化CO_2加氢合成甲醇的性能,同时结合N_2吸附-脱附(BET)、X射线衍射(XRD)、H_2程序升温还原(H_2-TPR)、程序升温脱附(H_2-TPD、CO_2-TPD)、N_2O滴定、X射线光电子能谱(XPS)、透射电子显微镜(TEM)等表征研究了不同助剂对CO_2催化加氢制甲醇的影响。结果表明,催化剂中的金属氧化物改变了SBA-15分子筛载体的孔径大小和比表面积;催化剂CuO-ZnO-MnO_2/SBA-15、CuO-Zn O-ZrO_2/SBA-15中铜的分散度(D_(Cu))和比表面积(A_(Cu))更大,表面CuO粒径更小,更易被还原;相比Mn-O簇,Zr-O簇为增强了碱性位点,提高了甲醇选择性。此外,CuO-ZnO-ZrO_2/SBA-15具有更高的氧空位浓度,催化活性更好,其甲醇选择性为25.02%,与CuO-ZnO/SBA-15、CuO-ZnO-Mn O_2/SBA-15相比分别提高了28%和136.9%,催化效果最好。     

Screening of coulomb impurities in graphene

We calculate exactly the vacuum polarization charge density in the field of a subcritical Coulomb impurity, Z|e|/r, in graphene. Our analysis is based on the exact electron Green's function, obtained by using the operator method, and leads to results that are exact in the parameter Zalpha, where alpha is the "fine-structure constant" of graphene. Taking into account also electron-electron interactions in the Hartree approximation, we solve the problem self-consistently in the subcritical regime, where the impurity has an effective charge Z(eff), determined by the localized induced charge. We find that an impurity with bare charge Z=1 remains subcritical, Z(eff)alpha<1/2, for any alpha, while impurities with Z=2, 3 and higher can become supercritical at certain values of alpha.     

Spectra of Stimulated Electromagnetic Emission of the Ionosphere Upon Sweeping of the Pump Wave Frequency Near Gyroharmonics. I. Experimental Results

We present the results of experimental studies of the spectra of the stimulated electromagnetic emission excited in the ionosphere by powerful radio waves during the pump wave frequency sweeping near the forth (n = 4) and fifth (n = 5) harmonics of the electron cyclotron frequency nf _ce. The frequency sweep was carried out for long (continuous) pumping in vertical and inclined directions (at 14° and 18° south of the zenith), as well as for the pulse diagnostic wave both with and without additional pumping far from the gyroharmonics. The dependences of the spectral features of the stimulated electromagnetic emission on the ratio between the pump-wave frequency f ₀ (or on the diagnostic-wave frequency f_DW) and nf _ce were analyzed. It is found that near the multiple gyroresonance, different spectral features of the stimulated emission are quenched at the same frequency for different pump-wave frequencies. For a sufficiently large inclination of the pump wave beam from the vertical direction, the intensity of the stimulated electromagnetic emission is notably decreased for f ₀ ≲ nf _ce as compared with f ₀ > nf _ce. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 6, pp. 461–476, June 2008.     

分光度法测定蒙药广枣中的微量铁

采用浓硝酸和高氯酸的混合消化法处理广枣样品,盐酸羟胺将铁(Ⅲ)还原成铁(Ⅱ),在pH为6的条件下,用分光度法测定铁含量,校准曲线回归方程为:y=0.00275779 0.18968x,(r=0.9999),回收率为99.5%-102.3%,RSD为0.72%,广枣中铁含量为66.5902μg/g.该方法操作简单,重现性好.