A Comprehensive Approach for Estimating Hydraulic Quantities in a Multi-branched Estuarine System

Despite many previous investigations, there is no theoretically justifiable equation to determine the freshwater discharge, tidal velocity, and salinity in a complex estuary that contains several branches. In this study, the longitudinal distributions of freshwater and salinity concentration in multi-branched estuaries are investigated using a mathematical model, considering the energy balance by frictional head loss and the salt balance by diffusion and advection in a one-dimensional steady-state condition. We attempt to obtain the time-mean freshwater discharge rate quantitatively at a junction where the main flow separates into two branches. The salinity distribution along each branch is calculated by following the dispersion coefficient equation previously proposed for a single estuary. The salinity field is divided into the near-coast region and the upstream region, because in each segment the inland velocity varies according to the tidal flux. For computing the tidal velocity, we propose the Burgers equation and the Hoph-Cole transformation. The theoretical results obtained by these equations were found to be in good agreement with a set of observed data in the Red River estuary system.     

π-ELECTRON CONTENTS OF RINGS IN THE DOUBLE-HEXAGONAL-CHAIN HOMOLOGOUS SERIES (PYRENE,ANTHANTHRENE AND OTHER ACENOACENES)

Abstract

Recently three methods for calculating the π-electron content of rings of benzenoid hydrocarbons were put forward: one based on the consideration of Kekuléstructural formulas, and the other two based on an analogous treatment of the Clar aromatic sextet formulas. These three methods are applied to the homologous series consisting of two condensed acene chains (whose first members are pyrene, anthanthrene, peri-naphthacenonaphthacene, …), leading to basically identical results. In contrast to acenes (in which the partition of π-electrons into rings is uniform), in the double-hexagonal-chain species the partition of π-electrons is highly non-uniform. The electron content monotonically decreases, in opposite directions, along the two acene chains, being maximal in the least annelated rings. Some other generally valid regularities in the π-electron properties of the double–hexagonal–chain benzenoids are also pointed out.     

An Analytical Model for Evaluating Outage and Handover Probability of Cellular Wireless Networks

We consider stochastic cellular networks where base stations locations form a homogeneous Poisson point process and each mobile is attached to the base station that provides the best mean signal power. The mobile is in outage if the signal-to-noise-plus-interference ratio falls below some threshold. The handover decision has to be made if the mobile is in outage during several time slots. The outage probability and the handover probabilities are evaluated taking into account the effect of path loss, shadowing, Rayleigh fast fading, frequency factor reuse and conventional beamforming. The main assumption is that the Rayleigh fast fading changes at each time slot while other network components remain static during the period of study.     

美国线路共享政策的实施与现状

线路共享指的是，用户除了从自己归属的本地电话公司（ILEC）以外还能选择从其它运营公司（主要指CLEC）为自己提供数据业务，并且不必安装第二条电话线。线路共享为现有电话线路上开展数据业务竞争铺平了道路，它在美国被视作能否成功开放DSL市场的关键因素。本文对美国针对DSL发展问题出台线路共享政策以及线路共享政策出台后的实施状况加以报道。对于我国制定线路共享政策和实施管理提供参考。     

Ion-milled waveguide lenses and lens arrays in GaAs

The authors discuss ion-milled planar waveguide lenses in GaAs which exhibit a considerably higher efficiency than that previously reported for those lenses and near diffraction-limited spot size. The authors also report the performance characteristics of these latest lenses, including single lenses and lens array of analog Fresnel, chirp grating, and hybrid types as well as a collimation-Fourier transformation lens-pair, together with the detailed design and fabrication procedures. A simple theoretical model for the lens efficiency is also formulated to assist in the lens design. Ion milling has been shown to be a simple and versatile technique for fabrication of waveguide lenses in GaAs and applicable to any other substrate material. Such ion-milled waveguide lenses should facilitate realization of a variety of monolithically integrated optic device modules and circuits in GaAs and other related substrates with applications to communications, signal processing, and computing     

Selective IR absorption in molecular nanofilms

We have formulated a microscopic theory of optical properties of ultrathin molecular films (nanofilms), i.e. quasi 2D systems parallel to XY planes bounded by two surfaces. Exposure of nanofilms to the external electromagnetic fields has result in creation of excitons - but different than bulk ones. Harmonic exciton states were calculated using the method of two-time, retarded, temperature dependent Green’s functions. It has been shown that two types of optical excitations can occur: bulk and surface exciton states. Exciton energy dispersion law shows discrete behavior with non-zero values. Analysis of the dielectric properties of these crystalline systems for low exciton concentration shows that the permittivity strongly depends on boundary parameters and the thickness of the film. In addition, permittivity shows very narrow and discrete dependence of external electromagnetic field frequency, which is a consequence of both resonance and quantum size effects. Influences of boundary conditions on optical characteristics (through analyses of dynamical absorption coefficient) of these nanostructures were specially and in details explored.     

Pattern nulling in difference pattern by amplitude control

A method of placing nulls in directions of any unwanted radio frequency interference (RFI) sources in the difference pattern of a phased array by controlling the current amplitudes is discussed. Thus one can now achieve pattern nulling in both the sum and difference patterns by amplitude control and can therefore carry out the minimization of RFI noise independently of the maximization of the desired signal. The method therefore provides an efficient alternative approach to the design of adaptive phased arrays.     

Minimisation of mutual coupling effect on doa estimation by using guard elements

The accuracy of the direction-of-arrival (DOA) estimation using a receiving phased array is degraded by the mutual coupling between the antenna elements. It is shown that by putting guard elements on each end of a linear array the DOA estimate error is reduced.     

Optical add-drop multiplexers with low crosstalk

We propose and demonstrate three new optical add-drop multiplexer (OADM) architectures with simple and compact configuration and excellent crosstalk performance. The OADMs use a single multiport optical circulator and either one or two narrow-band fiber Bragg gratings, depending on the crosstalk requirement     

Nonlinear analysis techniques of block masonry walls in nuclear power plants

Concrete masonry walls have been used extensively in nuclear power plants as non-load bearing partitions serving as pipe supports, fire walls, radiation shielding barriers, and similar heavy construction separations. When subjected to earthquake loads, these walls should maintain their structural integrity. However, some of the walls do not meet design requirements based on working stress allowables. Consequently, utilities have used non-linear analysis techniques, such as the arching theory and the energy balance technique, to qualify such walls. This paper presents a critical review of the applicability of non-linear analysis techniques for both unreinforced and reinforced block masonry walls under seismic loading. These techniques are critically assessed in light of the performance of walls from limited available test data. It is concluded that additional test data are needed to justify the use of nonlinear analysis techniques to qualify block walls in nuclear power plants.