A sequential quadratic programming-based algorithm for optimization of gas networks

British Gas uses a complex, heavily looped network of pipes and controllable units (compressors and regulators) to transmit gas from coastal supply terminals to regional demand points. Computer algorithms are required for efficient management of the system. This paper describes an algorithm for optimal control over periods of up to a day. The problem is large scale and highly nonlinear in both objective function and constraints. The method is based on Sequential Quadratic Programming and takes account of the structure of the pipeflow equations by means of a reduced gradient technique which eliminates most of the variables from the quadratic subproblems. The latter involve only simple bound constraints, which are handled efficiently by a conjugate gradient-active set algorithm. Trust region techniques permit use of the exact Hessian, preserving sparsity. More general constraints are handled at an outer level by a truncated augmented Lagrangian method. Results are included for some realistic problems. The algorithm is generally applicable to problems with a control structure.     

关于建立火力发电厂燃煤混合最优化数学模型的探讨

本文从煤的元素分析成分、工业分析成分和煤的工业特性对运行设备安全及经济性的影响出发,阐述了建立火力发电厂燃煤混合最优化数学模型的思路,并提出了许多有针对性的建议。     

Image segmentation towards new image representation methods

Very low bit-rate video coding has recently become one of the most important areas of image communication and a large variety of applications have already been identified. Since conventional approaches are reaching a saturation point, in terms of coding efficiency, a new generation of video coding techniques, aiming at a deeper “understanding” of the image, is being studied. In this context, image analysis, particularly the identification of objects or regions in images (segmentation), is a very important step. This paper describes a segmentation algorithm based on split and merge. Images are first simplified using mathematical morphology operators, which eliminate perceptually less relevant details. The simplified image is then split according to a quad tree structure and the resulting regions are finally merged in three steps: merge, elimination of small regions and control of the number of regions.     

Stress concentration and fatigue of profiled reinforcing steels

Stress concentrations arise from profiles of ribbed reinforcing steel bars and in this study the results of calculated stress concentration factors (SCF), by using finite element method, are related to the fatigue test results. It is apparent that the degree of confinement of a ribbed bar embedded in concrete not only affects the magnitude of the ultimate bond stress but also the bond stress-slip relation. Thus the rib geometry or profile pattern is designed for optimum bond characteristics and not for fatigue considerations. However the rib geometry influences the fatigue performance through the SCFs arising from the root radius, width and flank angles of the profiles. It is shown that these latter factors have a significant influence on the fatigue behaviour of reinforcing steel bars.     

Mathematical model and discrete artificial Bee Colony algorithm for distributed integrated process planning and scheduling

With the development of the globalization of economy and manufacturing industry, distributed manufacturing mode has become a hot topic in current production research. In the context of distributed manufacturing, one job has different process routes in different workshops because of heterogeneous manufacturing resources and manufacturing environments in each factory. Considering the heterogeneous process planning problems and shop scheduling problems simultaneously can take advantage of the characteristics of distributed factories to finish the processing task well. Thus, a novel network-based mixed-integer linear programming (MILP) model is established for distributed integrated process planning and scheduling problem (DIPPS). The paper designs a new encoding method based on the process network and its OR-nodes, and then proposes a discrete artificial bee colony algorithm (DABC) to solve the DIPPS problem. The proposed DABC can guarantee the feasibility of individuals via specially-designed mapping and switching operations, so that the process precedence constraints contained by the network graph can be satisfied in the entire procedure of the DABC algorithm. Finally, the proposed MILP model is verified and the proposed DABC is tested through some open benchmarks. By comparing with other powerful reported algorithms and obtaining new better solutions, the experiment results prove the effectiveness of the proposed model and DABC algorithm successfully.     

Prediction of venturi scrubber efficiency used in an updraft gasifier cleaning train

The performance of a venturi scrubber in the removal of tar from gas in updraft gasification has been studied. The gasifier has been operated with a husk feed rate of 1.6 × 10^?4 kg/s. The venturi scrubber has been operated at a superficial gas velocity of 56.4 m/s at the throat. A wide variety of scrubbing liquids having surface tensions ranging from 0.026 to 0.072 N/m have been used. The Q_g/Q_l, has been varied in the range of 1000–8000. The tar separation efficiency η has been found to vary from 51 to 98.5%. A mathematical model, assuming steady-state operation, has been developed considering very high pseudosolubility of tar in the scrubbing liquids. The predicted values of η have been compared with experimental results. The model satisfactorily explains the tar removal efficiency of the venturi for Q_g/Q_l values ranging from 4000 to 8000 for all scrubbing liquids. The following correlation has been developed for predicting venturi scrubber efficiency: .     

弧形连铸机结晶器四连杆机构振动误差计算

分析了DANIELI连铸机结晶器四连杆振动装置的结构型式，并在文献[1]的基础上建立了适合该振动装置振动误差计算的数学模型，并用FORTRAN语言编制了计算程序，验证计算表明该数学模型准确适用。     

一种计算孕育衰退时间的数学模型

确定孕育衰退时间对于正确制定工艺措施、提高铸件质量具有重要意义。以异质形核理论为基础,建立了孕育剂扩散衰退模型,得到了计算衰退时间的表达式。结果表明:孕育衰退时间与孕育剂中有效形核相的溶质扩散系数成反比,与有效形核相的半径及该相中的溶质浓度等参数有关。最后对该模型进行了验证,结果表明该模型与相关试验结果基本符合。     

不锈钢AOD转炉精炼过程数学模拟初探

对不锈钢AOD转炉精炼过程数学模拟作了初步研究,注意到该侧顶复吹精炼过程的物理和化学特性,考虑体系的质量和热量衡算,以及添加渣料、废钢、合金料等操作、精炼过程的不等温状态、钢液和熔渣质量的变化等因素的影响,提出了一个针对整个精炼过程的数学模型。基于设计的操作模式,以该模型对120 t AOD转炉内奥氏体不锈钢的整个精炼过程,包括氧化（脱碳）和还原过程作了模拟和估算,与工艺设计给出的参照数据作了比较。     

Multi-dimensional transient mathematical simulator of blast furnace process based on multi-fluid and kinetic theories

The ironmaking blast furnace is regarded as one of the biggest and most complex industrial reactors, because it includes various materials like gas, lump granular materials, liquids and powders and more than 30 major reactions and phase changes in a single reaction vessel. The mathematical simulator of this process developed in this study used the multi-fluid treatment as its framework, since the motions of these materials were governed by different flow mechanisms. The rates of the interactions among the phases and the chemical reactions were evaluated based on kinetic theories. The model successfully reproduced the fields of velocity, temperature and reaction in the furnace and its validity was confirmed. The simulator was also applied to a novel operation, namely the top gas recycling combined with the carbon-composite iron-ore charging and the waste plastics injection, and the advantages in furnace efficiency and environmental load were quantitatively indicated.