基体改进-石墨炉原子吸收光谱法测定海水样品中痕量的铜

用石墨炉原子吸收光谱法测定海水中痕量铜.对基体改进剂进行了筛选,采用HNO3-酒石酸体系,克服了海水基体的干扰,并对试剂进行了空白对照实验.在确定了升温程序的基础上,用标准加入法测定样品.使用国家标准溶液作为质控样,对方法的精密度和准确性做了验证.     

Polycaprolactone biopolymer thin films obtained by matrix assisted pulsed laser evaporation

We report the successful deposition of polycaprolactone polymer by MAPLE using a KrF* excimer laser (λ = 248 nm, τ = 7 ns). According to FTIR spectra the deposited films have similar chemical structure to the dropcast material. The fluence plays a key role in optimizing the performances of MAPLE-synthesized polycaprolactone structures. We demonstrated that MAPLE allows for controlling the morphology of films to the level required in targeted drug delivery of pharmacologic agents.     

Matrix assisted pulsed laser evaporation of poly(d,l-lactide) thin films for controlled-release drug systems

We report the successful deposition of the porous polymer poly(d,l-lactide) by matrix assisted pulsed laser evaporation (MAPLE) using a KrF* excimer laser (248 nm, τ = 7 ns) operated at 2 Hz repetition rate. The chemical structure of the starting materials was preserved in the resulting thin films. Fluence played a key role in optimizing our depositions of the polymer. We demonstrated MAPLE was able to improve current approaches to grow high quality thin films of poly(d,l-lactide), including a porosity control highly required in targeted drug delivery.     

Simulation of optical field in laser resonators cavity by eigenvector method

In this paper, an Eigenvector method (EM) for the calculation of optical resonator modes and beam propagation is introduced, in which the transit matrix of an optical resonator is obtained by dividing the mirror into finite grids based on the Fresnel–Kirchoff diffractive integral equation. Then, the eigenvectors, representing the multimode characteristics of the resonator, can be calculated by solving the integral matrix eigenequation. The merits of EM include that the considerably simpler procedure of solution of eigenvectors of the matrix eigenequation replaces the complicated iteration in traditional methods, and there is no dependence on the initial field distribution, and a number of modes can be derived once and the discrimination capability of the resonator can be evaluated easily. The examples using EM to simulate con-focal resonators with small or large Fresnel numbers are given, and the calculated results, well matched with Fox–Li method or Lagueree–Gaussian approximation analytical solution, prove that EM is highly feasible and reasonable.     

体上二次矩阵方程的解

本文得到了体上二次矩阵方程XAY= B有解的充要条件.并给出了当r(A)= r(B)时矩阵方程XAY= B的通解.     

Index minimization of differential-algebraic equations in hybrid analysis for circuit simulation

Modern modeling approaches for circuit analysis lead to differential-algebraic equations (DAEs). The index of a DAE is a measure of the degree of numerical difficulty. In general, the higher the index is, the more difficult it is to solve the DAE. The index of the DAE arising from the modified nodal analysis (MNA) is determined uniquely by the structure of the circuit. Instead, we consider a broader class of analysis method called the hybrid analysis. For linear time-invariant electric circuits, we devise a combinatorial algorithm for finding an optimal hybrid analysis in which the index of the DAE to be solved attains the minimum. The optimal hybrid analysis often results in a DAE with lower index than MNA.      

Double peaks on ac magnetization in a superconducting Pb-porous glass nanocomposite

Studies of temperature dependences of ac magnetization were carried out for a superconducting lead-porous glass nanocomposite. Double peaks were found on the imaginary part of ac magnetization which were accompanied with double steps on the real part. The lower-temperature anomalies in ac magnetization differed noticeably when they were obtained upon cooling and warming. The double peaks were treated as two phase transitions in the vortex system: the liquid-solid transition which occurs close to the onset of superconductivity and solid-solid one which is triggered by superconductivity in confined lead islands.     

Markovian trees: properties and algorithms

In this paper we introduce a structure called the Markovian tree (MT). We define the MT and explore its alternative representation as a continuous-time Markovian Multitype Branching Process. We then develop two algorithms, the Depth and Order algorithms to determine the probability of eventual extinction of the MT process. We show that both of these algorithms have very natural physically intuitive interpretations and are analogues of the Neuts and U algorithms in Matrix-analytic Methods. Furthermore, we show that a special case of the Depth algorithm sheds new light on the interpretation of the sample paths of the Neuts algorithm.     

Matrix effect for several derivatives of benzene in water by solid phase microextraction (SPME)

Summary Levels of several derivatives of benzene were examined in natural surface water (river Zala, West-Hungary) by solid phase micro extraction. Results from the river water samples were compared to the results from spiked double distilled water. The difference in extraction efficiency is termed a “matrix effect”. Large matrix effect causing the change of extraction efficiency experienced in this study. Relationship was found between the matrix effect and TOC, TIC, suspended and the dissolved matter content. Presented at Balaton Symposium on High Performance Methods, Siófok, Hungary, September, 1–3, 1999     

Impact of sideband harmonic pattern on losses in laminated non-oriented steel

Losses in laminated non-oriented steel under the effect of two high harmonic clusters, caused by voltage excitation typical of two-level pulse-with-modulated (PWM) DC-link and space-vector modulated (SVM) matrix converters, were analyzed. The predicting method proposed, which incorporates anisotropy of loss K_a and grain size g_s, describes the magnetizing process within the steel by the means of Poisson statistical distribution. Results are then compared to losses determined by Bertotti's model. The two methods confirmed that spreading of sideband harmonics in the kilohertz range can reduce harmonic losses by up to 40% at low power frequencies.