低维的Frobenius 型半单Hopf 代数

Let k be an algebraically closed field of characteristic zero.This paper proves that semisimple Hopf algebras over k of dimension 66,70 and 78 are of Frobenius type.     

动态光谱提取方法的对比研究

针对现有的频域法和单沿法这两种动态光谱提取方法进行了对比与研究.理论及实验结果表明,虽然两种方法提取动态光谱的角度不同,但其本质是相同的:源于动态光谱的基本原理、信号统计特性和平均作用的利用;对于周期、幅值较稳定的脉搏波,两种方法都能够提取高精度的动态光谱;相比较频域法,单沿法能够更好地抑制手指的抖动、光纤探头压力的改...     

Single photon frequency up-conversion and its applications

Optical frequency up-conversion is a technique, based on sum frequency generation in a non-linear optical medium, in which signal light from one frequency (wavelength) is converted to another frequency. By using this technique, near infrared light can be converted to light in the visible or near visible range and therefore detected by commercially available visible detectors with high efficiency and low noise. The National Institute of Standards and Technology (NIST) has adapted the frequency up-conversion technique to develop highly efficient and sensitive single photon detectors and a spectrometer for use at telecommunication wavelengths. The NIST team used these single photon up-conversion detectors and spectrometer in a variety of pioneering research projects including the implementation of a quantum key distribution system; the demonstration of a detector with a temporal resolution beyond the jitter limitation of commercial single photon detectors; the characterization of an entangled photon pair source, including a direct spectrum measurement for photons generated in spontaneous parametric down-conversion; the characterization of single photons from quantum dots including the measurement of carrier lifetime with escalated high accuracy and the demonstration of the converted quantum dot photons preserving their non-classical features; the observation of 2nd, 3rd and 4th order temporal correlations of near infrared single photons from coherent and pseudo-thermal sources following frequency up-conversion; a study on the time-resolving measurement capability of the detectors using a short pulse pump and; evaluating the modulation of a single photon wave packet for better interfacing of independent sources. In this article, we will present an overview of the frequency up-conversion technique, introduce its applications in quantum information systems and discuss its unique features and prospects for the future.     

Coefficients of Wronskian Hermite polynomials

We study Wronskians of Hermite polynomials labeled by partitions and use the combinatorial concepts of cores and quotients to derive explicit expressions for their coefficients. These coefficients can be expressed in terms of the characters of irreducible representations of the symmetric group, and also in terms of hook lengths. Further, we derive the asymptotic behavior of the Wronskian Hermite polynomials when the length of the core tends to infinity, while fixing the quotient. Via this combinatorial setting, we obtain in a natural way the generalization of the correspondence between Hermite and Laguerre polynomials to Wronskian Hermite polynomials and Wronskians involving Laguerre polynomials. Lastly, we generalize most of our results to polynomials that have zeros on the p-star.     

The bullwhip effect in supply chain networks

This paper analyzes the propagation and amplification of order fluctuations (i.e., the bullwhip effect) in supply chain networks operated with linear and time-invariant inventory management policies. The supply chain network is allowed to include multiple customers (e.g., markets), any network structure, with or without sharing information. The paper characterizes the stream of orders placed by any supplier for any stationary customer demand processes, and gives exact formulas for the variance of the orders placed and the amplification of order fluctuations. The paper also derives robust analytical conditions, based only on inventory management policies, to predict the presence of the bullwhip effect for any network structure, any inventory replenishment policies, and arbitrary customer demand processes. Numerical examples show that the analytical results accurately quantify the bullwhip effect; managerial insights are drawn from the analysis. The methodology presented in this paper generalizes those in previous studies for serial supply chains.     

Fluctuating characteristics of radiative source term in hydrogen turbulent jet diffusion flame

The laminar flamelet model in combination with joint probability density function transport equation of mixture fraction and turbulence frequency is used to simulate turbulent jet diffusion flames of hydrogen. The frequency distributions of radiative source terms are calculated for four important infrared bands of water vapor. The results show that, for the given ensemble, about 95% samples of radiative source term for each band locate within the region of ±3.0 standard deviation of the mean radiative source term. Due to the different relation between band intensity parameters and temperature for every band, the symmetrization of frequency distributions for each band is different.     

Stimulated four-photon mixing and efficient polychromatic visible light generation in SiO2-based single-mode optical fibers pumped at 1.319 μm

The generation of near-infrared and intense visible light through stimulated multi-wave mixing processes in single-mode silica-based optical fibers pumped by a Q-switched and mode-locked Nd:YAG laser operated at 1.319 μm is described. The experimental results show that intense infrared light around 1.2 μm is produced via selp-hase-matched four-photon mixing at the minimum group velocity dispersion region of pure SiO₂-core and P₂O₅-doped silica fibers. In the visible spectral region, from 580 nm to 600 nm, 20 W peak power 100-ps pulses were generated by pumping single spans of single-mode P₂O₅-doped and undoped SiO₂-core fibers with 1.319-μm laser pulses. The signal light generated in such fibers propagated in the LP₀₂ fiber mode and exhibited a threshold power that depended upon the fiber length and a critical length that was power dependent. Also, it exhibited an asymmetrical spectrum of a few nanometers bandwidth, with a long tail toward high frequencies. For GeO₂-doped silica-based fibers, a multiple-wavelength visible signal propagating in several high-order fiber modes was generated.     

Improvements in drug purity determination by capillary electrophoresis using UV-absorption and LIF-detection with a UV-laser

Summary In drug purity determinations by capillary electrophoresis using UV-detection generally a relative high concentration of the main compound has to be injected. Principles how to handle overloading effects are described. NXX-066 is a drug with a native fluorescence which made it possible to use of CE system equipped with a LIF-detection unit. Monitoring drug purity determination with LIF detection results in an improved limit of quantification of the impurities and/or opens a possibility to avoid an overloaded main peak. A frequency doubled (FRED) argon ion laser set at 244 nm was used as excitation source in drug purity determination with the LIF-detection unit and the chemicals used were therefore carefully chosen in order to minimize the background noise level, which easily is enhanced when fluorescence detection is performed in the UV-range. The separation of the fluorescent NXX-066 analogues proved to be a difficult task, but an adequate resolution was obtained when β- and γ-cyclodextrins was added as structural selectors and the separation window was expanded by the use of a repressed/reversed electroosmotic flow. A comparison of the separation capability for the UV-detection system and the laser induced fluorescence detection system was performed, showing that the overloading effects of the main peak can be removed using the CE-LIF system and thereby obtain a substantially improved resolution of the analogues. A comparison of LC-UV and CE-UV for drug purity determination of a crude product from, synthesis of NXX-066 is also included in this paper where a good correlation of the results were obtained. Presented at the 8th. International Symposium on High Performance Capillary Electrophoresis, Jan. 21–25 1996, Orlando, USA.     

AC loss measurements on model Bi-2223 conductors

Measurements of the AC loss in applied magnetic fields at 77 K have been made on model composite Bi-2223 conductors. A vibrating sample magnetometer (VSM) and a dual Hall sensor magnetometer (HSM) were used to cover the frequency range from below 0.01 Hz to over 250 Hz at AC fields up to 0.05 T rms. The VSM was limited to the frequency range below 0.2 Hz. A comparison of the two measurement techniques was possible at intermediate frequencies. The samples consisted of vertical stacks of well separated flat filaments of superconductor in Ag and Ag-alloy matrix, allowing a range of filament coupling conditions to be explored.     

AC losses in multifilamentary HTS-composite tapes based on BiPbSrCaCuO

Some results of AC loss measurements are presented for 19, 61, 127-filamentary Bi-2223/Ag tapes prepared by the ‘powder-in-tube' method. All measurements have been made at T=77 K under sinusoidal transport current with frequency in the range of 30–600 Hz and the current amplitude up to 30 A. The measurements have been carried out both in self field conditions and at the external magnetic field applied to the tape at the different angles. The dependencies of the AC losses on current amplitude and frequency have been obtained. It is found that for all tapes the current amplitude dependencies of the AC losses show good agreement with the Norris prediction for an elliptical or strip geometry. The AC loss dependencies on frequency were linear. The measurements of AC losses in external magnetic field show that the change of AC losses is only through the change of the critical current. So the transport AC losses in the tapes are the ‘saturation losses' that is they are different from classic hysteresis losses.