An Optical,Dual-Beam,Automated Medium Resolution Spectropolarimeter for the Vainu Bappu Telescope

Fabrication of an optical dual-beam spectropolarimeter as an add-on facility to an existing astronomical spectrograph at the Vainu Bappu Telescope is described. The polarimetric optics consists of a superachromatic Pancharatnam design half-wave plate and a modified Glan-Taylor polarizing beam splitter. Instrumental response, calibration and characterization of the system are presented. Performance of the spectropolarimeter has been assessed based on the results of observations of polarized and unpolarized standard stars. The attainable accuracy of the instrument is found to be dependent on the S/N of the data. The present data set yields an accuracy of ±0.5% at 4000 Å and ±0.3% at 7500 Å, at a spectral resolution of 7.2 Å. Analysis of spectropolarimetric data is systematically covered for removal of instrumental errors. The spectropolarimetric reduction software (SPRS), extremely versatile, user friendly and compatible with the IRAF image processing package, was developed for reducing spectropolarimetric data. The empirical relation by Serkowski (IAU Symposium 52, Interstellar Dust and Related Topics, J. M. Greenberg and H. C. van de Hulst (eds.), Dordrecht, Reidel, 1975, p. 145) for wavelength dependence of polarization due to interstellar medium has been fitted to the data for the star HD 43384 (9 Gem). Our result shows a polarization larger by 0.49% from Hsu and Berger (ApJ 262, 1982, 732). We attribute this difference to the long term variation in P for this star.     

Simultaneous optimization of the performance of flotation circuits and their simplification using the jumping gene adaptations of genetic algorithm-II: More complex problems

The binary-coded elitist non-dominated sorting genetic algorithm with the modified jumping gene operator (NSGA-II-mJG) is used to obtain global optimal solutions of flotation circuits. Several single-objective and multi-objective optimization problems are solved using the interconnecting cell linkage parameters (fraction flow rates) and the mean cell residence times as the decision variables. In the single-objective problem, the overall recovery of the concentrate stream is maximized for a desired grade of the concentrate. Two two-objective optimization problems are then solved. In one, the number of non-linking streams and the overall recovery of the concentrate are maximized simultaneously. This gives several simple circuits in a systematic manner with only marginally lower recoveries. In the other two-objective optimization problem, the overall recovery of the concentrate is maximized while the total cell volume is minimized. A three-objective problem (maximization of the overall recovery of the concentrate, maximization of the number of non-linking streams and minimization of the total cell volume) is then solved. All the problems constrain the grade of the product to lie at a fixed value. Finally, a complex and computationally intensive four-objective optimization problem is solved. The solution of several practical optimization problems in this study helps develop useful insights into the optimal solutions.     

Reduced-order optimal control of water flooding using proper orthogonal decomposition

Model-based optimal control of water flooding generally involves multiple reservoir simulations, which makes it into a time-consuming process. Furthermore, if the optimization is combined with inversion, i.e., with updating of the reservoir model using production data, some form of regularization is required to cope with the ill-posedness of the inversion problem. A potential way to address these issues is through the use of proper orthogonal decomposition (POD), also known as principal component analysis, Karhunen–Loève decomposition or the method of empirical orthogonal functions. POD is a model reduction technique to generate low-order models using ‘snapshots’ from a forward simulation with the original high-order model. In this work, we addressed the scope to speed up optimization of water-flooding a heterogeneous reservoir with multiple injectors and producers. We used an adjoint-based optimal control methodology that requires multiple passes of forward simulation of the reservoir model and backward simulation of an adjoint system of equations. We developed a nested approach in which POD was first used to reduce the state space dimensions of both the forward model and the adjoint system. After obtaining an optimized injection and production strategy using the reduced-order system, we verified the results using the original, high-order model. If necessary, we repeated the optimization cycle using new reduced-order systems based on snapshots from the verification run. We tested the methodology on a reservoir model with 4050 states (2025 pressures, 2025 saturations) and an adjoint model of 4050 states (Lagrange multipliers). We obtained reduced-order models with 20–100 states only, which produced almost identical optimized flooding strategies as compared to those obtained using the high-order models. The maximum achieved reduction in computing time was 35%.     

Multiobjective optimization for performance‐based seismic design of steel moment frame structures

The performance‐based seismic design of steel special moment‐resisting frame (SMRF) structures is formulated as a multiobjective optimization problem, in which conflicting design criteria that respectively reflect the present capital investment and the future seismic risk are treated simultaneously as separate objectives other than stringent constraints. Specifically, the initial construction expenses are accounted for by the steel material weight as well as by the number of different standard steel section types, the latter roughly quantifying the degree of design complexity related additional construction cost; the seismic risk is considered in terms of maximum interstory drift demands at two hazard levels with exceedance probabilities being 50% and 2% in 50 years, respectively. The present formulation allows structural engineers to find an optimized design solution by explicitly striving for a desirable compromise between the initial investment and seismic performance. Member sizing for code‐compliant design of a planar five‐story four‐bay SMRF is presented as an application example using the proposed procedure that is automated by a multiobjective genetic algorithm. Copyright © 2004 John Wiley & Sons, Ltd.     

三峡库区坡地资源优化利用模式与途径

三峡库区土地资源以山丘地为主,耕地又以坡旱地为主。其中>2 5°的陡坡耕地为2 6 7×10 4hm2 ,占库区耕地总量的18.2 %。研究表明,三峡库区粮食产量的5 6 %来自坡耕地,同时库区泥沙量的6 6 %也来自坡耕地。三峡大坝蓄水,移民后靠安置,对坡耕地利用的压力更大。坡地资源的优化利用,在库区农业生产、移民安置,以及生态环境建设方面都具有重要的意义和价值。基于土地资源优化利用原理和生态设计的理念,提出库区土地资源优化利用应突出生态效益、经济主导、产业协调、区域特色等4种模式,并针对当前库区土地资源利用中的主要问题,提出了相应的优化利用途径和对策     

边坡位移监测的若干技术问题

本文探讨了影响边坡位移监测精度的若干主要技术问题,认为只有选择恰当的地表位移监测基准,并对监测方案、监测站的布设和监测周期的设计等技术问题进行优化,才能满足边坡变形监测的要求。因此本文在此基础上,建议使用多种监测手段,建立立体监测系统,同时监测地表和地下位移,有助于全面反映边坡的变形破坏情况,从而为边坡的稳定性分析和滑坡预测预报提供科学依据。     

无限终端线性二次调节器最优输出反馈律

线性二次调节器问题在现代控制理论中占有重要地位。该文针对状态调节器最优反馈律结构复杂、不便工程实现等问题，着重讨论了无限终端带有输出方程的状态调节器的最优输出反馈律，还跟踪讨论了无限终端输出调节器的最优反馈律。所得结论可降低调节器的复杂程度，便于工程实现。     

一种基于均值比率和最佳熵的SAR影像边缘检测方法

针对比率边缘检测算子提出了一种自动确定阈值的方法,该方法引入最佳熵的理论到SAR边缘检测中,把基于比率的边缘检测均值比率影像分割成边缘和非边缘两类。此方法执行起来简单、快速,无需人工干预,能避免人为因素的影响。     

Variational solution about over-determined geodetic boundary value problem and its related theories

A new solving method for Laplace equation with over-determined geodetic boundary conditions is pro- posed in the paper, with the help of minimizing some kinds of quadratic functional in calculus of variation. At first, the so-called variational solution for over-determined geodetic boundary value problem is defined in terms of principles in calculus of variation. Then theoretical properties related with the solution are derived, especially for its existence, uniqueness and optimal approximation. And then the computational method of the solution is discussed, and its expression is exhibited under the case that all boundaries are spheres. Finally an arithmetic example about EGM96 gravity field model is given, and the computational results show that the proposed method can efficiently raise accuracy to deal with gravity data. In all, the variational solution of over-determined geodetic boundary value problem can not only fit to deal with many kinds of gravity data in a united form, but also has strict mathematical basements.     

东昌湖优化引水量计算模型研究

在综合考虑东昌湖的景观旅游、生态环境和工业供水等主要功能对水质、水量要求的基础上，建立了东昌湖优化引水量计算模型，对不同代表年各个月的需要调用黄河水量（通过平原水库谭庄水库调用）进行了分析计算。分析计算结果对东昌湖在满足生态系统良性循环和保证供水的前提下，科学调引黄河水量提供了依据。