阿莫西林分散片溶出度光纤化学传感在线过程检测

采用双波长法消除赋形剂的干扰,利用六通道光纤化学传感原位过程分析仪(FOCSDT)在线监测阿莫西林分散片溶出度。FOCSDT的平均校准曲线方程为y=188.38x+0.7607,回归系数r为0.9998。阿莫西林分散片的溶出数据与中国药典(Ch.P)方法对照无显著性差异。FOCSDT法无需取液、稀释等手工操作,能实时监测药物溶出全过程,为速释制剂内在质量的检测提供良好的手段。     

基于Mie散射的CO_2激光大气传输特性测量

为了更准确地计算大气透过率,在Mie散射理论基础上,分析了雷达系统设计中需考虑的大气透过率的经验计算公式,指出了该经验公式的不足。考虑大气分析软件MODTRAN自身的优点,采用经验公式和软件计算相结合的方式计算大气透过率,给出了MODTRAN计算结果的修正表达式。在该理论指导下,进行了CO2激光大气传输实验。由于没有考虑大气湍流,理论计算和实验结果存在一定偏差,但不影响本文方法的实用性。实验测量显示,激光器出口处光斑能量抖动比为6.18%,而在50m和1km处能量抖动比分别为8.3%和50.2%,表明随着传输距离增加,能量抖动比增大。除掉激光器本身输出能量抖动外,在50m和1km处由大气传输造成的能量抖动比分别为2.12%和44.02%。实验结果提示,水平传输1km时能量抖动已相当剧烈,所以对更远距离的激光传输,自适应光学补偿显得尤为重要。     

Performance of a four‐element Si drift detector for X‐ray absorption fine‐structure spectroscopy: resolution, maximum count rate,and dead‐time correction with incorporation into the ATHENA data analysis software

The performance of a four‐element Si drift detector for energy‐dispersive fluorescence‐yield X‐ray absorption fine‐structure measurements is reported, operating at the National Institute of Standards and Technology beamline X23A2 at the National Synchrotron Light Source. The detector can acquire X‐ray absorption fine‐structure spectra with a throughput exceeding 4 × 10⁵ counts per second per detector element (>1.6 × 10⁶ total counts per second summed over all four channels). At this count rate the resolution at 6 keV is approximately 220 eV, which adequately resolves the Mn Kα and Kβ fluorescence lines. Accurate dead‐time correction is demonstrated, and it has been incorporated into the ATHENA data analysis program. To maintain counting efficiency and high signal to background, it is suggested that the incoming count rate should not exceed ～70% of the maximum throughput.     

Blocking probability analysis of survivable routing in WDM optical networks with/without sparse-wavelength conversion

In this paper, a new algorithm for wavelength assignment has been proposed and its performance is evaluated in terms of blocking probability and fairness. It has been shown that the proposed algorithm offers the least blocking probability. The blocking performance of wavelength division multiplexing (WDM) network has been analyzed for the network having 10 nodes and for varying loads. As the load per link (in Erlangs) increases, the blocking probability increases. The result shows that the performance of first-fit algorithm is better than random algorithm whereas the proposed algorithm offers the least blocking.     

Gaussian soliton generation using a 1.3 μm optical pulse in a micro-ring resonator for a new DWDM enhancement

We present a novel system of a Gaussian soliton generation using a 1.30 μm optical pulse in a nonlinear micro-ring resonator system, which can be used to form the soliton pulse trains within the new wavelength band. By using the suitable parameters, the soliton pulse trains with the center wavelength at 1.30 μm can be generated after the intense Gaussian pulse is input into the nonlinear micro-ring resonator system. The initial pulse bandwidth is enlarged and the signal amplified by the nonlinear Kerr effects type within the ring resonator. The simulation values are used associating with the practical device parameters, whereas the obtained results have shown that the wavelength enhancement of the center wavelength can be achieved. Furthermore, the maximum soliton output power of 12 W is obtained, which is available to perform the long-distance communication link. The common problem of soliton dispersion is minimized by the zero dispersion condition in this case. The major advantage of the proposed system is that the dense wavelength division of the center wavelength with the spectral width of 7.0 pm (10⁻¹⁵ m) and the free spectrum range of 400 pm can be generated and achieved. This is available for the used/installed wavelength enhancement, which can provide more available channel capacity in the existed public optical network.     

Performance analysis of optical wavelength switching network using multiple output light source

In this paper a 32×32 optical wavelength switching network using the multi-channel and multi-wavelength spectrum-sliced light source is presented where the 2×2 optical-switching elements are utilized in dilated Benes and modified dilated Benes configurations, respectively. The system performances in bit-error rate, especially for the effects of intraband crosstalk, are analyzed in details for the two type networks. Through the simulation studies, the dilated Benes shows better performances than the modified dilated Benes configuration.     

Fractional diffusion-type equations with exponential and logarithmic differential operators

We deal with some extensions of the space-fractional diffusion equation, which is satisfied by the density of a stable process (see Mainardi et al. (2001)): the first equation considered here is obtained by adding an exponential differential (or shift) operator expressed in terms of the Riesz–Feller derivative. We prove that this produces a random component in the time-argument of the corresponding stable process, which is represented by the so-called Poisson process with drift. Analogously, if we add, to the space-fractional diffusion equation, a logarithmic differential operator involving the Riesz-derivative, we obtain, as a solution, the transition semigroup of a stable process subordinated by an independent gamma subordinator with drift. Finally, we show that an extension of the space-fractional diffusion equation, containing both the fractional shift operator and the Feller integral, is satisfied by the transition density of the process obtained by time-changing the stable process with an independent linear birth process with drift.     

Stationary convection–diffusion equation in an infinite cylinder

We study the existence and uniqueness of a solution to a linear stationary convection–diffusion equation stated in an infinite cylinder, Neumann boundary condition being imposed on the boundary. We assume that the cylinder is a junction of two semi-infinite cylinders with two different periodic regimes. Depending on the direction of the effective convection in the two semi-infinite cylinders, we either get a unique solution, or one-parameter family of solutions, or even non-existence in the general case. In the latter case we provide necessary and sufficient conditions for the existence of a solution.     

Non‐homogeneous infinitely many sites discrete‐time model with exact coalescent

Kingman's coalescent is among the most fertile concepts in mathematical population genetics. However, it only approximates the exact coalescent process associated with the Wright–Fisher model, in which the ancestry of a sample does not have to be a binary tree. The distinction between the approximate and exact coalescent becomes important when population size is small and time has to be measured in discrete units (generations). In the present paper, we explore the exact coalescent, with mutations following the infinitely many sites model. The methods used involve random point processes and generating functionals. This allows obtaining joint distributions of segregating sites in arbitrary intervals or collections of intervals, and generally in arbitrary Borel subsets of two or more chromosomes. Using this framework it is possible to find the moments of the numbers of segregating sites on pairs of chromosomes, as well as the moments of the average of the number of pairwise differences, in the form that is more general than usually. In addition, we demonstrate limit properties of the first two moments under a range of demographic scenarios, including different patterns of population growth. This latter part complements results obtained earlier for Kingman's coalescent. Finally, we discuss various applications, including the analysis of fluctuation experiments, from which mutation rates of biological cells can be inferred. Copyright © 2009 John Wiley & Sons, Ltd.     

Preliminary results for the design,fabrication,and performance of a backside-illuminated avalanche drift detector

The detection of low-level light is a key technology in various experimental scientific studies. As a photon detector, the silicon photomultiplier （SiPM） has gradually become an alternative to the photomultiplier tube （PMT） in many applications in high-energy physics, astroparticle physics, and medical imaging because of its high photon detection efficiency （PDE）, good resolution for single-photon detection, insensitivity to magnetic field, low operating voltage, compactness, and low cost. However, primarily because of the geometric fill factor, the PDE of most SiPMs is not very high; in particular, for those SiPMs with a high density of micro cells, the effective area is small, and the bandwidth of the light response is narrow. As a building block of the SiPM, the concept of the backside-illuminated avalanche drift detector （ADD） was first proposed by the Max Planck Institute of Germany eight years ago; the ADD is promising to have high PDE over the full energy range of optical photons, even ultraviolet light and X-ray light, and because the avalanche multiplication region is very small, the ADD is beneficial for the fabrication of large-area SiPMs. However, because of difficulties in design and fabrication, no significant progress had been made, and the concept had not yet been verified. In this paper, preliminary results in the design, fabrication, and performance of a backside-illuminated ADD are reported; the difficulties in and limitations to the backside-illuminated ADD are analyzed.