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Candidate Attainable Regions for the Oxidative Dehydrogenation of n-Butane using the Recursive Constant Control (RCC) Policy Algorithm

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INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH 2009年第11期48卷 5211-5222页

作者： Milne, David Seodigeng, Tumisang Glasser, David Hildebrandt, Diane Hausberger, Brendon Univ Witwatersrand Ctr Mat & Proc Synth ZA-2050 Wits South Africa

Attainable region (AR) ideas have previously been used to identify candidate attainable regions (AR(C)s) for the oxidative dehydrogenation (ODH) of n-butane to butenes and butadiene and in so doing to identify the maximum possible yields of different hydrocarbon product. Because of the large dimensionality of the problem, it was not possible then to do a complete AR analysis. Among the configurations considered, it was found that the reactor configuration for the respective AR(C)s ill all instances was an inert membrane reactor (IMR) functioning as a differential side-stream reactor in which one of the reactants, oxygen, was introduced along the length of the reactor so as to maintain a very low and constant Value of its partial pressure. Nevertheless, despite producing high yields of product, extremely large and impractical residence times ensued. In this paper, a new tool, the recursive convex control (RCC) policy, is used to identify the AR(C)s in the full dimensional space. These AR(C)s showed excellent agreement with those previously published, and the optimal reactor structures presented in those publications have been confirmed albeit with different oxygen control parameters. The maximum yields are now achieved with very much lower residence times. These results also confirm the benefit from using the AR approach on problems where a full AR analysis is not possible.

关键词： BUTANE DEHYDROGENATION BUTADIENE CHEMICAL engineering MEMBRANE reactors HYDROCARBONS OXIDATION computer algorithms

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Prediction of intermetallic compounds

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RUSSIAN CHEMICAL REVIEWS 2009年第6期78卷 569-587页

作者： Burkhanov, G. S. Kiselyova, N. N. Russian Acad Sci AA Baikov Inst Met & Mat Sci Moscow 119991 Russia

The problems of predicting intermetallic compounds not yet synthesized are discussed. It is noted that the use of classical physicochemical analysis in the study of multicomponent metallic systems is associated with the complexity of presenting multidimensional phase diagrams. The use of modern information technology with application of computer pattern recognition method is a route to the prediction new intermetallics with specified properties. The algorithms used most often in these methods are briefly considered and the efficiency of their use for predicting new compounds is demonstrated. The bibliography includes 144 references.

关键词： INTERMETALLIC compounds PHASE diagrams CHEMICAL processes IMAGING systems in chemistry computer algorithms ANALYTICAL chemistry

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A MODIFIED PSO FOR LOW SIDELOBE CONCENTRIC RING ARRAYS SYNTHESIS WITH MULTIPLE CONSTRAINTS

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JOURNAL OF ELECTROMAGNETIC WAVES AND APPLICATIONS 2009年第11-12期23卷 1535-1544页

作者： Zhang, S. Gong, S. -X. Zhang, P. -F. Xidian Univ Natl Key Lab Antennas & Microwave Technol Xian 710071 Shaanxi Peoples R China

This paper describes a modified particle swarm optimization (MPSO) for the synthesis of the low sidelobe concentric ring arrays. The MPSO has been utilized to optimize the element placement in a concentric ring array to obtain the lowest peak sidelobe level (PSLL). And here the multiple optimization constraints include the array aperture, the minimum ring spacing and the element spacing in each ring. Unlike standard PSO using fixed corresponding relationship between the optimal variables and their coding, the MPSO utilized the coding resetting of optimal variables to avoid infeasible solution during the optimization process. Also, the proposed approach has reduced the size of the searching area of the PSO by means of indirect description of individual. The simulated results confirming the great efficiency and robustness of this algorithm are provided in this paper.

关键词： PARTICLE swarm optimization SWARM intelligence computer algorithms MATHEMATICAL optimization SIMULATION methods & models

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Simulation of dose deposition in stereotactic synchrotron radiation therapy: a fast approach combining Monte Carlo and deterministic algorithms

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PHYSICS IN MEDICINE AND BIOLOGY 2009年第15期54卷 4671-4685页

作者： Smekens, F. Freud, N. Letang, J. M. Adam, J-F Ferrero, C. Elleaume, H. Bravin, A. Esteve, F. Babot, D. Inst Natl Sci Appl CNDRI Nondestruct Testing Using Ionizing Radiat L F-69621 Villeurbanne France Inst Neurosci Grenoble INSERM U836 Equipe Rayonnement Synchrotron & Rech Med 6 Grenoble France Univ Grenoble 1 Grenoble France European Synchrotron Radiat Facil F-38043 Grenoble France Hop Michallon CHU Grenoble Unite IRM Grenoble France

A hybrid approach, combining deterministic and Monte Carlo (MC) calculations, is proposed to compute the distribution of dose deposited during stereotactic synchrotron radiation therapy treatment. The proposed approach divides the computation into two parts: (i) the dose deposited by primary radiation (coming directly from the incident x-ray beam) is calculated in a deterministic way using ray casting techniques and energy-absorption coefficient tables and (ii) the dose deposited by secondary radiation (Rayleigh and Compton scattering, fluorescence) is computed using a hybrid algorithm combining MC and deterministic calculations. In the MC part, a small number of particle histories are simulated. Every time a scattering or fluorescence event takes place, a splitting mechanism is applied, so that multiple secondary photons are generated with a reduced weight. The secondary events are further processed in a deterministic way, using ray casting techniques. The whole simulation, carried out within the framework of the Monte Carlo code Geant4, is shown to converge towards the same results as the full MC simulation. The speed of convergence is found to depend notably on the splitting multiplicity, which can easily be optimized. To assess the performance of the proposed algorithm, we compare it to state-of-the-art MC simulations, accelerated by the track length estimator technique (TLE), considering a clinically realistic test case. It is found that the hybrid approach is significantly faster than the MC/TLE method. The gain in speed in a test case was about 25 for a constant precision. Therefore, this method appears to be suitable for treatment planning applications.

关键词： RADIOTHERAPY SYNCHROTRON radiation RADIATION -- Dosage STEREOTAXIC techniques MONTE Carlo method computer algorithms SIMULATION methods & models HYBRID systems

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Fundamental Kinetic Modeling of Catalytic Reforming

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INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH 2009年第3期48卷 1107-1119页

作者： Sotelo-Boyas, Rogelio Froment, Gilbert F. Texas A&M Univ Artie McFerrin Dept Chem Engn College Stn TX 77843 USA

A fundamental kinetic model for the catalytic reforming process has been developed. The complex network of elementary steps and molecular reactions occurring in catalytic reforming was generated through a computer algorithm characterizing the various species by means of vectors and Boolean relation matrices. The algorithm is based on the fundamental chemistry occurring on both acid and metal sites of a Pt-Sn/Al2O3 catalyst. The number of rate coefficients for the transformations occurring on the metal sites was reduced by relating them to the nature of the involved carbon atoms. The single event concept was applied in the development of rate expressions for the elementary steps on the acid sites. This approach allows obtaining rate coefficients that are independent of the feedstock, owing to their fundamental chemical nature. The Levenberg-Marquardt algorithm was used to estimate the rate coefficients. The estimation was based on data reported from a previous naphtha reforming study in a fixed bed reactor with Pt-Sn/Al2O3 as a catalyst. The agreement between the experimental and estimated yields is excellent. The statistical tests were also satisfied. The kinetic model was used in pseudo-homogeneous and heterogeneous reactor models simulating an industrial three-bed adiabatic catalytic reformer with centripetal radial flow.

关键词： CATALYTIC reforming CHEMICAL kinetics computer algorithms METAL catalysts MATHEMATICAL models SIMULATION methods & models

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Modeling and visualization of lifecycle building performance assessment

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ADVANCED ENGINEERING INFORMATICS 2009年第4期23卷 396-417页

作者： Gursel, Ipek Sariyildiz, Sevil Akin, Oemer Stouffs, Rudi Delft Univ Technol Fac Architecture NL-2600 GA Delft Netherlands Carnegie Mellon Univ Sch Architecture Pittsburgh PA 15213 USA

Lifecycle building performance assessment (LBPA) ensures that buildings perform and operate as intended during building lifecycle. Such assessment activities are typically multi-phase and multi-disciplinary, and generate large amounts of information that need efficient management. During the lifecycle of one building, multiple assessment methods are employed semi-concurrently and with a great deal of information overlap between successive phases. This information is semantically rich and context-dependent, reflecting the local perspective that it exists within. Usage of separate and disconnected tools for each method results in information fragmentation and redundancy, posing problems for well-informed decision making. The objective of this research is to develop an integral reference model, CLIP (Computational support for Lifecycle Integral Performance assessment), that aims to improve the efficiency and quality of existing performance assessment practices. The model provides flexible, modular, and extensible data structures and algorithms for the representation, transformation, integration, and visualization of performance information. The initial results support the CLIP model's ability to deal with the local volatility and variation in the processes and information content that is being managed, while requiring further refinement and extension work to achieve a customized solution to fit in different contextual settings. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： BUILDINGS -- Performance BUILDING information modeling DECISION making DATA structures (computer science) computer algorithms MATHEMATICAL models SYSTEM analysis

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Incremental state based diagnosis

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ADVANCED ENGINEERING INFORMATICS 2009年第3期23卷 309-322页

作者： Coghill, George M. Wu, Guofu Univ Aberdeen Sch Nat & Comp Sci Aberdeen AB24 3UE Scotland Ilcom Ltd Shrewsbury Salop England

In this paper we present an incremental diagnostic engine: IMBDE. IMBDE utilises qualitative models, and combines an extended version of Nayak and Williams' ITMS (based on root antecedents) with an incremental version of Reiter's Hitting Set Algorithm to perform incremental state based diagnosis on dynamic process systems. The approach is demonstrated to work by application to an industrial process - an ammonia washer system. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： DECISION support systems ARTIFICIAL intelligence TRUTH maintenance systems QUALITATIVE research MANUFACTURING processes computer algorithms

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Large-Scale Identification and Quantification of Covalent Modifications in Therapeutic Proteins

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ANALYTICAL CHEMISTRY 2009年第20期81卷 8354-8364页

作者： Zhang, Zhongqi Amgen Inc Proc & Prod Dev Thousand Oaks CA 91320 USA

Covalent modifications on therapeutic proteins are traditionally monitored by chromatographic techniques, which quantify limited number of protein modifications at a time. In this report, computer algorithms for automated analyses of liquid chromatography/tandem mass spectrometry (LC/MS/MS) data for large-scale identification and quantification of known and unknown modifications are described. Peptide identification is achieved by comparing the experimental fragmentation spectrum to the predicted spectrum of each native or modified peptide. Peak areas of related peptide ions under their selected-ion chromatograms (SIC) are used for relative quantification of modified peptides. A matched window function is used to generate SIC for more reliable quantification. In an LC/MS/MS analysis of a tryptic digestion of an IgG2 monoclonal antibody, 1712 peptide ions were identified with a false-discovery rate of similar to 0.4%, and 227 modifications were identified and quantified. The accuracy of the mass spectrometry-based quantification is evaluated by comparing the abundance of different glycoforms determined by mass spectrometry to that determined by a fluorescence-based chromatography method. This large-scale method may potentially replace many chromatographic methods for assessing the quality attributes of therapeutic proteins.

关键词： PROTEINS -- Therapeutic use computer algorithms LIQUID chromatography TANDEM mass spectrometry CHROMATOGRAMS PEPTIDE synthesis

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Finding the Frequent Items in Streams of Data

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COMMUNICATIONS OF THE ACM 2009年第10期52卷 97-105页

作者： Cormode, Graham Hadjieleftheriou, Marios AT&T Labs Res Florham Pk NJ USA

The frequent items problem is to process a stream of items and find all those which occur more than a given fraction of the time. It is one of the most heavily studied problems in mining data streams, dating back to the 1980s. Many other applications rely directly or indirectly on finding the frequent items, and implementations are in use in large-scale industrial systems. In this paper, we describe the most important algorithms for this problem in a common framework. We place the different solutions in their historical context, and describe the connections between them, with the aim of clarifying some of the confusion that has surrounded their properties. To further illustrate the different properties of the algorithms, we provide baseline implementations. This allows us to give empirical evidence that there is considerable variation in the performance of frequent items algorithms. The best methods can be implemented to find frequent items with high accuracy using only tens of kilobytes of memory, at rates of millions of items per second on cheap modern hardware.

关键词： STREAMING technology (Telecommunications) SEARCH algorithms DATA mining computer algorithms INFORMATION science -- Statistical methods computer science

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Unified Simulation Evaluation for Mobile Broadband Technologies

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IEEE COMMUNICATIONS MAGAZINE 2009年第3期47卷 142-149页

作者： Gao, Yuehong Zhang, Xin Yang, Dacheng Jiang, Yuming Beijing Univ Posts & Telecommun Wireless Theories & Technol Lab Beijing Peoples R China Norwegian Univ Sci & Technol Ctr Quantifiable Qual Serv Syst Q25 Trondheim Norway NTNU Dept Telemat Trondheim Norway

System-level simulation has been widely used to evaluate system performance. Simulation methodologies have also been comprehensively discussed in different organizations or institutions. Most of the simulation methodologies proposed, however, mainly focus on one area of specific technologies. How to evaluate the performance of multiple air interface systems (e.g., cdma2000, WCDMA, WiMAX, ana their evolutions) in a fair and comprehensive manner has not been addressed extensively. This article presents a unified simulation methodology, including fading channel models, system configurations, and how to consider technology-dependent algorithms such as scheduling, overhead modeling, interference margin definition, and resource allocation based on system loading. This article uses this framework to compare three major existing radio technologies: cdma2000 1x EV-DO Rev. A, WCDMA HSPA, and mobile WiMAX based on 802.16e. Key simulation results based on our suggested system models and settings are presented and analyzed. It is shown that under our unified framework, the two CDMA systems exhibit higher spectrum efficiency than mobile WiMAX, especially on the downlink, while mobile WiMAX provides a higher peak rate.

关键词： MOBILE communication systems BROADBAND communication systems computer simulation computer systems ELECTROMAGNETIC interference IEEE 802.16 (Standard) ENGINEERING standards computer algorithms TELECOMMUNICATION

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