Removal of cationic dyes by poly(acrylamide-co-acrylic acid) hydrogels in aqueous solutions

Poly(acrylamide-co-acrylic acid (poly(AAm-co-AAc)) hydrogels prepared by irradiating with γ-radiation were used in experiments on swelling, diffusion, and uptake of some cationic dyes such as Safranine-O (SO) and Magenta (M). Poly(AAm-co-AAc) hydrogels irradiated at 8.0 kGy have been used for swelling and diffusion studies in water and cationic dye solutions. The maximum swellings in water, and SO, and M solutions observed are 2700%, 3500%, and 4000%, respectively. Diffusions of water and cationic dyes within hydrogels have been found to be non-Fickian in character. Adsorption of the cationic dyes onto poly(AAm-co-AAc) hydrogels is studied by the batch adsorption technique. The adsorption type was found Langmuir type in the Giles classification system. The moles of adsorbed dye for SO and M per repeating unit in hydrogel (binding ratio, r) have been calculated as 3834×10⁻⁶ and 1323×10⁻⁶, respectively. These results show that poly(AAm-co-AAc) hydrogels can be used as adsorbent for water pollutants such as cationic dyes.     

Identifiability issues of age–period and age–period–cohort models of the Lee–Carter type

The predominant way of modelling mortality rates is the Lee–Carter model and its many extensions. The Lee–Carter model and its many extensions use a latent process to forecast. These models are estimated using a two-step procedure that causes an inconsistent view on the latent variable. This paper considers identifiability issues of these models from a perspective that acknowledges the latent variable as a stochastic process from the beginning. We call this perspective the plug-in age–period or plug-in age–period–cohort model. Defining a parameter vector that includes the underlying parameters of this process rather than its realizations, we investigate whether the expected values and covariances of the plug-in Lee–Carter models are identifiable. It will be seen, for example, that even if in both steps of the estimation procedure we have identifiability in a certain sense it does not necessarily carry over to the plug-in models.     

A note on the integrality gap of an ILP formulation for the periodic maintenance problem

We address the integrality gap of the integer linear program introduced by Grigoriev et al. (2006) [3] for the periodic maintenance problem. We prove that the integrality gap of this program is bounded by a constant.     

公共资本对产出及私人资本的动态冲击效应研究

估算了我国总的资本存量和公共资本存量,并从资本存量的角度基于结构向量自回归模型(SVAR)研究了公共资本对私人资本和产出的动态影响.通过实证研究得出以下结论:1)在我国公共资本对私人资本具有先"挤入"后"挤出"的效应.给公共资本一个百分点的冲击,在第'三年使得私人资本增加0.5个百分点.2)产出对公共资本冲击的响应更加快速和直接,给公共资本一个百分点的冲击会使得产出在第2期时增长0.8个百分点,但是这种正的响应会逐渐减弱,并在第6期后不再显著.3)方差分解的结果表明,私人资本对产出的贡献率要大于公共资本对产出的贡献率,私人资本对产出贡献率的最大值为61%,而公共资本对产出贡献率的最大值为28%.     

向量自回归(VAR)模型中的识别问题——分析框架和文献综述

向量自回归模型(VAR)是时间序列计量经济学的标准分析工具。在VAR模型中施加长期或短期限制,使非限制的约化VAR模型成为协整(VECM)或结构协整向量自回归模型(SVECM)时,存在长期和短期结构识别问题。识别问题在以VAR为模型框架的实证分析中起到关键作用,因此是结构VAR模型研究中的一个重点。本文阐述VECM和SVECM模型中结构识别问题的理论框架,对有关文献进行综述,解释结构VAR模型在实证分析中的应用方法,简述这一领域的最新进展和研究方向。     

基于meta-analysis和等级全息建模的可信软件开发风险识别研究

对软件开发过程中的风险进行有效识别,是提升软件可信性的重要方法和手段.本文以面向可信的软件开发过程风险辨识为研究对象,采用meta-analysis方法,结合软件项目开发风险相关的文献,采取高频词提取的方法,得出了前20大风险,并对需求、用户、供应商等前10大风险进行了重点阐述.给出了可信软件风险识别的等级全息框架,以产品、项目管理、项目结果、属性等10个视角全息辨识可信软件开发过程中可能面临的风险,与等级可变的不同风险情景识别过程相结合,为可信软件的风险识别构建了系统的解决思路和框架.     

On some regularities in dynamic response of cyclic periodic structures

The paper deals with cyclic periodic structures modelling bladed disk assemblies of blades with friction elements for vibration damping. These elements placed between adjacent blades reduce the vibration amplitudes by means of dry friction resulting from centrifugal forces acting on the elements and relative displacements of the blades. However, the application of these friction elements results in an additional dynamical coupling which together with mistuning of some system parameters (e.g., blade eigenfrequency or contact parameters) may cause localization of vibration. In the present paper a linear approximation of such a system is investigated. The structure composed of cyclic periodic cells modelled each as a clamped-free beam interacting with each other by means of viscoelastic elements of complex stiffness is applied for dynamic system analysis. In case of free vibrations as well as in case of steady-state dynamic response to a harmonic pressure field, a perfect periodic structure and the structures with periodically mistuned parameters (blade eigenfrequencies and contact parameters) are studied. Some regularities in the dynamic response of the systems with mistuning have been noticed. Despite the fact that only a linear approximation has been used, the results and conclusions can be applied for models which describe the blade interaction in a nonlinear way.     

AN EXISTENCE THEOREM OF SOLUTIONS FOR SEMILINEAR ELLIPTIC EQUATIONS ON R~N

1991MRSubjectClassification35C15,58E50ConsiderthesernilinearellipticdifferentialequationInthestudyofllollliliearSchrodingerequations,nonlinearequationsofKleili~Gordolltypeall(1reaction-diffusiollequatiolls,sollltionsof(1)correspolldtostalldingwavesolutions.stroll(lill~(ortraveling)wavesolutionsandsteadystatesofthesystem.Manypapersdealtwiththeautonomouscasewhere5andfareindependentofatorwiththeradiallysynlluetriccasewherebandfdependonfi](see[1-4]andtheirreferences).Recentlytheperiodiccaseand…     

Tensor Sylvester matrices and the Fisher information matrix of VARMAX processes

The purpose of this paper is to develop compact expressions for the Fisher information matrix (FIM) of a Gaussian stationary vector autoregressive and moving average process with exogenous or input variables, a vector ARMAX or VARMAX process. We develop a representation of the FIM based on multiple Sylvester matrices. An extension of this representation yields another one but in terms of tensor Sylvester matrices. In order to obtain the results presented in this paper, the approach used in [A. Klein, G. Mélard, P. Spreij, On the resultant property of the Fisher information matrix of a vector ARMA process, Linear Algebra Appl. 403 (2005) 291-313] is extended.