Determination of silicon by an indirect atomic-absorption method using carbon-rod electrothermal atomization

An indirect procedure has been developed for the determination of trace amounts of silicon by atomic-absorption with carbon-rod electrothermal atomization. After dissolution, the silicon is extracted as silicomolybdic acid into a mixture of diethyl ether and pentan-1-ol (5 + 1). The co-extraction of excess of molybdate reagent is prevented by the addition of citrate, which also destroys phosphomolybdic and arsenomolybdic acids. The organic layer is washed with hydrochloric acid, mul quantities are transferred to the electrothermal atomizer and the molybdenum is measured. The method has been applied to analysis of several steels.     

LTE外辐射源雷达帧间模糊带分析与抑制

LTE (Long Term Evolution)信号具有大带宽、高覆盖率、强通用性等优点,是一种新型的外辐射源雷达机会照射源。该文从FDD-LTE (Frequency Division Duplexing Long Term Evolution)信号结构入手,探讨了该信号作为第三方机会照射源的模糊函数特性;根据实测FDD-LTE信号,阐述了模糊函数中帧间模糊带抑制的必要性,并对该帧间模糊带的形成机理进行了详细的分析,分析结果表明LTE信号结构中的确定性特征既是引起模糊带的主要因素,同时也是信号相干积累的主要能量来源。对此,该文提出了基于OFDM (Orthogonal Frequency Division Multiplexing)符号子载波系数归一化的帧间模糊带抑制方法,该方法能够在抑制帧间模糊带的同时,又不影响信号相干积累进行目标探测。仿真和实测结果验证了该抑制方法的有效性,为LTE外辐射源雷达目标探测奠定了基础。      

Robust pulses for high fidelity non-adiabatic geometric gate operations in an off-resonant three-level system

We propose a method to design pulses in a resonant three-level system to enhance the robustness of non-adiabatic geometric gate operations. By optimizing the shape of the pulse envelope, we show that the gate operations are more robust against frequency detuning than they are with Gaussian and square pulses. Our method provides a way to design pulses that can be employed in a system where robustness against frequency variations or inhomogeneous broadening is required, and may be extended to ensure robustness against other physical imperfections such as intensity fluctuations and random noises.     

基于MHD的磁射流抛光中流场的分析与模拟

从理论上分析了磁射流抛光中的磁场与流场的相互作用,构建了磁射流抛光的冲击射流模型,基于磁流体动力学对磁射流抛光过程的紊动冲击射流进行数值模拟,得到了磁射流抛光过程的连续流场和射流在工件壁面上的压力、速度、紊动强度分布。通过比较射流抛光和磁射流抛光的数值计算结果,分析了磁流变效应对射流稳定性的影响,从射流的流场、速度、紊动强度等方面分析射流在磁场中稳定的原因。     

Quantum Circuits and Schr?dinger’s Cat States

Quantum systems that are confined to circuit geometries are called quantum circuits. Macroscopic superconducting circuits are quantum circuits which can be modelled using a Quantisation by Parts scheme based on the macroscopic wave function approach of Feynman. This paper studies the circuit composed of an input wire and an output plate. We find that in order to achieve a consistent theory of supercurrent flow we have to generalize the quantisation by parts scheme to quantise in a path space. The generalized theory predicts a current flow down the wire into the plane. In addition to a current flowing radially outwards in the plane, the theory allows a circulating current round the origin. Strikingly, the circulating current can flow clockwise or anti-clockwise in such a way as to generate a magnetic moment of magnitude half of a Bohr magneton for an orbiting electron in an atom and a magnetic flux half that of the magnetic flux quantum of a superconducting ring. There is also the possibility of a macroscopic superposition of the two states of opposing circulating currents resembling a Schr?dinger’s cat situation. Furthermore, we outline a setup involving an external magnetic field that may allow experimental tests of the theory.     

Measurement of thermal radiative properties of penguin down and other fibrous materials using FTIR

Penguins live in the extremely cold Antarctic. Understanding the thermal radiative properties of penguin down may help us to develop super insulating materials. In this study, Fourier transform infrared spectroscopy (FTIR) was applied to measure the thermal radiative properties of penguin down and compare them with those of other fibrous materials. It was found that penguin and duck down are superior to other fibrous materials, such as polyester, Thinsulate and wool, at the same fibre volume fraction, in shielding the radiative heat transmission, largely due to their fine fibre diameter. There is an optimum fibre diameter at which the fibrous materials are at their best in blocking thermal radiation. The fibre diameter of penguin down is very close to this optimum value. The study further found that the relationship between the effective thermal radiative conductivity and fibre fineness may be better fitted with a quadratic curve.     

Synthesis of Human Cancer Associated Globo-H (MBr1) Glycosylamino Acid: Some Mechanistic and Conformational Reinvestigations

The synthesis of an extended globo-H (MBr1 antigen) in the form of a glycosylamino acid is reported. By careful NMR analysis, we found an interesting conformational "flip" on the E ring of some synthetic intermediates. An explanation offered for the successful [3+3] coupling of ABC acceptor 11 and DEF donor 10 possessing a C4 free hydroxyl to produce β-galactoside in azaglycosidations is reinforced.     

三头季铵盐阳离子表面活性剂合成菱形十二面体介孔二氧化硅单晶

由于介孔二氧化硅单晶规整的外观形貌和有序的内部孔道结构性能, 使其在微激光器件领域具有十分重要的潜在应用. 试着用高电荷密度的阳离子三头季铵盐表面活性剂(C18-2-3-1)作模板剂, 用正硅酸四乙酯作无机前驱体, 在硫酸介质中通过调变有机-无机物种之间的协同组装作用, 成功地合成了具有简单立方相Pm3n结构的介孔二氧化硅单晶. 扫描电子显微镜(SEM)观察到这种介孔二氧化硅单晶具有菱形十二面体形貌, X射线衍射(XRD)和透射电子显微镜(TEM)测试结果证实这种介孔单晶属于简单立方Pm3n对称结构. 氮气吸附数据测得这种单晶具有较大的BET比表面积(550 cm2/g), 较大的孔体积(BJH 0.20 cm3/g)和孔径(BJH 2.4 nm).