G/M/1 queues with delayed vacations

We considerG/M/1 queues with multiple vacation discipline, where at the end of every busy period the server stays idle in the system for a period of time called changeover time and then follows a vacation if there is no arrival during the changeover time. The vacation time has a hyperexponential distribution. By using the methods of the shift operator and supplementary variable, we explicitly obtain the queue length probabilities at arrival time points and arbitrary time points simultaneously.     

Moving eccentric crack in a piezoelectric strip bonded to elastic materials

Summary  The steady-state of a propagation eccentric crack in a piezoelectric ceramic strip bonded between two elastic materials under combined anti-plane mechanical shear and in-plane electrical loadings is considered in this paper. The analysis based on the integral transform approach is conducted on the permeable crack condition. Field intensity factors and energy release rate are obtained in terms of a Fredholm integral equation of the second kind. It is shown for this geometry that the crack propagation speed has influence on the dynamic energy release rate. The initial crack branching angle for a PZT-5H piezoceramic structure is predicted by the maximum energy release rate criterion. Received 23 January 2001; accepted for publication 18 October 2001     

Efficient Analysis of Millimeter Wave Ferrite Circulators by the GMRES Iterative Algorithm

The finite element method (FEM) combined with the perfectly matched layers (PML) is given for simulation of waveguide ferrite circulators. The generalized minimal residual (GMRES) iterative method is applied to solve such sparse large non-symmetric system of linear equations resulting from the use of edge-based finite element method. The formulation of FEM and the algorithm of GMRES method are described in detail. The reflection and insertion losses of millimeter wave waveguide circulator are analyzed and the results are compared with those obtained from literature.     

Field Trial of 40 Gbit/s ETDM Prototype System over 219 km of Installed Single Mode Fiber

Transmission of 40Gbit/s NRZ signal was successfully demonstrated over 219km of installed SMF in KT's Daejeon area network. After transmission, the measured power penalty was 0.5dB for all the tributary channels.     

Thermogelling behaviors of poly(caprolactone‐b‐ethylene glycol‐b‐caprolactone) triblock copolymer in the presence of hyaluronic acid

In this article, we studied the effect of hyaluronic acid (HA) on thermogelation of poly(caprolactone‐b‐ethylene glycol‐b‐caprolactone) (PCL‐PEG‐PCL) aqueous solution designed as an injectable system for prevention of postsurgical tissue adhesion. The PCL‐PEG‐PCL triblock copolymers were simply synthesized by ring‐opening polymerization of ε‐caprolactone (CL) in the presence of PEG as a polymeric initiator. The synthesized copolymers were confirmed by proton nuclear magnetic resonance (¹H‐NMR) spectroscopy. Possible interactions between HA and PCL‐PEG‐PCL triblock copolymers in the blend were evaluated by Fourier‐transform infrared spectroscopy (FTIR). The effect of HA on the micellization of PCL‐PEG‐PCL aqueous solution was investigated by dye solubilization method and electrophoretic lighting scattering (ELS) spectrophotometer. Also, the thermogelling behaviors of the PCL‐PEG‐PCL triblock copolymers in the presence of HA and their mechanism were investigated by test tube inverting method, ¹³C‐NMR, ¹H‐NMR, Advanced Rheometic Expansion System (ARES), and differential scanning calorimetry (DSC). The PCL‐PEG‐PCL/HA blend aqueous solutions undergo the sol‐gel‐sol transition in response to an increase in temperature (10–60 °C) and the gelation of the PCL‐PEG‐PCL was rather accelerated by HA. Presumably, this accelerated gelation seems to arise from the attractive interactions between them and the effect of chain confinement in the micelle corona region. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3629–3637, 2008     

Digital watermarking technique for holography interference patterns in a transform domain

A digital holography interference pattern generated by a computer calculation (computer generated hologram, CGH) is one of the most expensive contents and its usage is being expanded. Thus, it is highly necessary to protect the ownership of a digital hologram. This paper introduces a watermarking scheme, a method to protect the ownership of digital holograms using the DCT domain data as the ones to be watermarked. This scheme shows very high imperceptibility and strong robustness against the anticipated attacks. We expect that the conclusions of this paper will be a very useful basis for further work in the area of electronic watermarking schemes for the digital holograms.     

Nucleon charge radius from QCD sum rules

The proton and neutron electric radii are calculated within QCD using the sum rules method for processes with small momentum transfers. The agreement with experimental values is good for the proton radius and somewhat poorer for the neutron one due to the numerical smallness.     

A conditional limit construction of the normal probability density

Summary It is shown that a normal probability density can be characterized as a limit of conditional probability densities of i.i.d. uniform random variables.