Order Modeling Approach Research Articles

Relationship between Conformational Dynamics and Electron Transfer in a Desolvated Peptide. Part I. Structures

The structures, dynamics and energetics of the protonated, derivatized peptide DyeX-(Pro)(4)-Arg(+)-Trp, where "Dye" stands for the BODIPY analogue of tetramethylrhodamine and X is a (CH(2))(5) linker, have been investigated using a combination of modeling approaches in order to provide a numerical framework to the interpretation of fluorescence quenching data in the gas phase. Molecular dynamics (MD) calculations using the new generation AMOEBA force field were carried out using a representative set of conformations, at eight temperatures ranging from 150 to 500 K. Force field parameters were derived from ab initio calculations for the Dye. Strong electrostatic, polarization and dispersion interactions combine to shape this charged peptide. These effects arise in particular from the electric field generated by the charge of the protonated arginine and from several hydrogen bonds that can be established between the Dye linker and the terminal Trp. This conclusion is based on both the analysis of all structures generated in the MD simulations and on an energy decomposition analysis at classical and quantum mechanical levels. Structural analysis of the simulations at the different temperatures reveals that the relatively rigid polyproline segment allows for the Dye and Trp indole side chain to adopt stacking conformations favorable to electron transfer, yielding support to a model in which it is electron transfer from tryptophan to the dye that drives fluorescence quenching.

A general approach to develop reduced order models for simulation of solid oxide fuel cell stacks

Numerical models for solid oxide fuel cells (SOFCs) are needed in system modeling studies of fuel cell-based power generation systems. A reduced order modeling approach based on response surface techniques is developed for SOFC stacks. This approach creates a numerical model that can quickly compute desired performance variables of interest based on the stack's input parameter state. The developed method first carefully samples the multidimensional design space based on the input parameter ranges, automatically evaluates an existing detailed stack model at each of the sampled points, and performs regression for selected performance variables of interest to determine the response surfaces. After error analysis to ensure that sufficient accuracy is established for the response surfaces, they are then implemented in a calculator module for use by the system-level software. The benefit of this modeling approach is that it is sufficiently fast for integration with system modeling software while still providing high fidelity information about the internal distributions of key variables in the fuel cell. This paper describes the sampling, regression, sensitivity, error, and principal component analysis to identify the most appropriate methods for simulating a planar SOFC stack.

Investigation of the Effects of Length to Depth Ratio on Open Supersonic Cavities Using CFD and Proper Orthogonal Decomposition

Simulations of supersonic turbulent flow over an open rectangular cavity are performed to observe the effects of length to depth ratio (L/D) of the cavity on the flow structure. Two-dimensional compressible time-dependent Reynolds-averaged Navier-Stokes equations with k-ω turbulence model are solved. A reduced order modeling approach, Proper Orthogonal Decomposition (POD) method, is used to further analyze the flow. Results are obtained for cavities with several L/D ratios at a Mach number of 1.5. Mostly, sound pressure levels (SPL) are used for comparison. After a reduced order modeling approach, the number of modes necessary to represent the systems is observed for each case. The necessary minimum number of modes to define the system increases as the flow becomes more complex with the increase in the L/D ratio. This study provides a basis for the control of flow over supersonic open cavities by providing a reduced order model for flow control, and it also gives an insight to cavity flow physics by comparing several simulation results with different length to depth ratios.

Simulation of Heat and Mass Transport in a Square Lid-Driven Cavity with Proper Generalized Decomposition (PGD)

The aim of this study is to apply proper generalized decomposition (PGD) to solve mixed-convection problems with and without mass transport in a two dimensional lid-driven cavity. PGD is an iterative reduced order model approach which consists of solving a partial differential equation while seeking the solution in separated form. Comparisons with results in the literature and with results from a standard solver are make. For the case of a mixed-convection problem without mass transfer, three Richardson numbers are considered, Ri = 0.1, Ri = 1, and Ri = 10. In this case, PGD is seven times faster than the standard solver with Ri = 10 with a similar accuracy. For the case with mass transfer, simulations are done with different Lewis numbers, Le = 5, Le = 25, and Le = 50, and with different value of the ratio N between the solutal and the thermal Grashoff numbers. In this case, too, PGD is ten times faster than the standard solver.

Modeling and optimization of bioethanol production via a simultaneous saccharification and fermentation process using starch

AbstractBACKGROUNDBioethanol is an attractive alternative fuel because it is less carbon‐intensive than oil and is also a renewable bio‐based energy source. The aim of this study is to present a mathematical modeling approach in order to describe the simultaneous saccharification and fermentation process of the yeast Saccharomyces cerevisiae YPB‐G for the production of bioethanol using starch.RESULTSAn unstructured model was proposed for model parameters that are independent of initial operating conditions, but have a highly predictive capability that can be used in process optimization and control. The predictions of the proposed models were compared with experimental data and against the results of other models presented in the literature.CONCLUSIONA technique of gradually expanding the search domain combined with a genetic algorithm was proposed to successfully speed up the optimization computation of parameter estimation. Compared with an earlier model presented in the literature, the proposed model shows more versatility with fewer numbers of parameters and fixed values of parameters, and provides a satisfactory prediction capability. The proposed model was used to investigate the process optimization of batch culture. Numerical results may provide various process alternatives for planning the productivity of bioethanol. © 2012 Society of Chemical Industry

Modelo Híbrido GJR-GARCH Nebuloso para a Previsão da Volatilidade em Mercados de Ações

A previsão da volatilidade dos retornos de ativos financeiros é uma abordagem desafiadora e tem atraído a atenção de participantes do mercado, reguladores e acadêmicos nos anos recentes. Este artigo propõe um modelo GJR-GARCH nebuloso para a previsão da volatilidade dos índices S&P 500 e Ibovespa. O modelo combina os conceitos de sistemas de inferência nebulosos e a abordagem GJR-GARCH para considerar os príncipios de variância condicional, efeitos de alavancagem e agrupamentos de volatilidade, em que as flutuações são associadas por similaridade. Além disso, um algoritmo de evolução diferencial (ED) é sugerido para solucionar o problema de estimação dos parâmetros do modelo GJR-GARCH nebuloso. Os resultados indicaram que o método proposto permitiu uma melhor capacidade de previsão da volatilidade em comparação com modelos da família GARCH e com um modelo GARCH nebuloso recentemente proposto na literatura. Além disso, o algoritmo de ED considerado obteve soluções ótimas com uma rápida taxa de convergência.

Cast iron cutting with nano TiN and multilayer TiN-CrN coated inserts

During the past decade great success has been achieved in the development of duplex and multilayer multi-functional surface systems. Among these surface systems outstanding properties have nanoscale multilayer coatings. Within the framework of the M3-2S project funded in the 7th European Framework Programme, several nanoscale multilayer coatings have been developed and investigated for experimental and industrial validation. This paper shows the performance of TiN and TiN/CrN nanoscale multilayer coatings on WC cutting inserts when machining GJL250 cast iron. The thin films have been deposited by cathodic arc evaporation in an industrial PVD system. The multilayer deposition characteristic and its properties are shown. The inserts have been investigated in systematic cutting experiments of cast iron bars on a turning machine specifically equipped for force measurements, accompanied by wear determination. Furthermore, equivalent experiments have been carried out on an industrial turning unit. Industrial validation criteria have been applied to assess the comparative performance of the coatings. The choice of the material and the machined parts is driven by an interest in automotive applications. The industrial tests show the need to further optimise the multi-scale modelling approach in order to reduce the lead time of the coating development as well as to improve simulation reliability.

Application of Kriging and radial basis function in power electronic module wire bond structure reliability under various amplitude loading

This paper discusses life time prediction of wire bond structure in a power electronic module based on computational approach that integrates methods for high fidelity analysis, reduced order modelling, and life time prediction using reduced order model. This methodology is demonstrated for the design of a wire bond structure in a power electronic module with aim of reducing the chance of failure due to the wire bond lift off in power electronic module when a random load is applied to the aluminium wire. In particular, wire bond reliability of the power module related to the thermal fatigue material degradation of aluminium wire is one of the main concerns. In the power electronic module reliability, understanding the performance, reliability and robustness of wire bond is a key factor for the future development and success of the power electronic module technology, because wire bond lift off failure ignites other catastrophic failures.The main focus in this study is on the application of reduced order modelling techniques and the development of the associated models for fast evaluation and analysis. The discussion is on methods for approximate response surface modelling based on interpolation techniques using Kriging and radial basis functions. The reduced order modelling approach uses prediction data for the electro-thermo-mechanical behaviour of the power module wirebond design obtained through non-linear transient finite element simulations, in particular for the fatigue life-time of the aluminium wire attached to the silicon chip of the wire in the module. The reduced order models are used for the analysis of predicting the life time of the wire bond structure under random load. One of the widely used cycle counting algorithm, so called rainflow counting algorithm is utilised to count the cycles of temperature profile at the a specific point of the wire bond structure in a power electronic module. Using the cycle results from rainflow algorithm mean life time of the wire bond structure is predicted by a linear cumulative damage model such as Palmgren–Miner rule. This model is utilised to predict the mean fatigue life of the wire bond structure.

Using Electronic Resources to Support Problem-Based Learning

Students acquire skills in problem solving and critical thinking through the process as well as team work on problem-based learning courses. Many courses have started to involve the online learning environment and integrate these courses with electronic resources. Teachers use electronic resources in their classes. To overcome the problem of the limited teaching resources, electronic resources can help students to engage in self-learning more easily. This study addresses electronic resources usage in problem-based learning. Therefore, the aim of this article is to investigate the relationship between the capability to use electronic resources and problem-based learning performance. A quantitative analysis was conducted through the structural equation modeling approach in order to indicate the direction and relationship between these constructs. To conclude, this study suggests that tutor support, peer participation, and internet search capability should be conceptualized as forming part of an important learning context. Further, the results indicate that both peer participation and internet search capability are required to facilitate the development of problem-solving skills.

Reduced Order Thermal Modeling of Data Centers via Distributed Sensor Data

In this paper, an effective and computationally efficient proper orthogonal decomposition (POD) based reduced order modeling approach is presented, which utilizes selected sets of observed thermal sensor data inside the data centers to help predict the data center temperature field as a function of the air flow rates of computer room air conditioning (CRAC) units. The approach is demonstrated through application to an operational data center of 102.2 m2 (1100 square feet) with a hot and cold aisle arrangement of racks cooled by one CRAC unit. While the thermal data throughout the facility can be collected in about 30 min using a 3D temperature mapping tool, the POD method is able to generate temperature field throughout the data center in less than 2 s on a high end desktop personal computer (PC). Comparing the obtained POD temperature fields with the experimentally measured data for two different values of CRAC flow rates shows that the method can predict the temperature field with the average error of 0.68 °C or 3.2%. The maximum local error is around 8 °C, but the total number of points where the local error is larger than 1 °C, is only ∼6% of the total domain points.

Improved methodologies for the design of maneuver for stability and control simulations

With many modern fighter aircraft experiencing unpredicted flight dynamics during flight tests, recent research has focused on developing methodologies for incorporating computational fluid dynamics into the aircraft development process. The goal of this approach is to identify configurations susceptible to stability and control issues early in the design process. Previous research has primarily focused on full aircraft configurations, however, to increase the rate of development the current study focused on a two-dimensional NACA0012 airfoil. The two-dimensional NACA0012 airfoil has the advantage of reducing the computational cost by orders of magnitude compared to full scale aircraft simulations, while still providing complicated aerodynamics at high angles of attack. Computationally predicted lift coefficients from a number of newly developed training maneuvers were used to generate reduced order aerodynamic loads models. For evaluation, these models were compared to generated static and dynamic validation data. Methods of improving both the computational training maneuver and the reduced order modeling approach are suggested.

A Statistical Characterization of the Effects of Mistuning in Multistage Bladed Disks

A great deal of research has been conducted on the effects of small random variations in structural properties, known as mistuning, in single stage bladed disks. Due to the inherent randomness of mistuning and the large dimensionality of the models of industrial bladed disks, a reduced order modeling approach is required to understand the effects of mistuning on a particular bladed disk design. Component mode mistuning (CMM) is an efficient compact reduced order modeling method that was developed to handle this challenge in single stage bladed disks. In general, there are multiple stages in bladed disk assemblies, and it has been demonstrated that for certain frequency ranges accurate modeling of the entire bladed disk assembly is required because multistage modes exist. In this work, a statistical characterization of structural mistuning in multistage bladed disks is carried out. The results were obtained using CMM combined with a multistage modeling approach previously developed. In addition to the statistical characterization, a new efficient classification method is detailed for characterizing the properties of a mode. Also, the effects of structural mistuning on the characterization of the mode is explored.

Modeling P(3HB) production by Bacillus megaterium

AbstractBACKGROUND: The poly(3‐hydroxybutyrate)—P(3HB)—is a polyester synthesized by many bacteria and stored as an energy reserve material in the cell cytoplasm as water‐insoluble inclusions. The aim of this research was to present a mathematical modeling approach in order to describe the culture kinetics of the bacterium Bacillus megaterium for the production of poly(3‐hydroxybutyrate).RESULTS: Four different models were proposed, differing in the expressions used for specific growth and polymer production rates. The predictions of these models were compared with experimental data and against the results of other models reported in the literature.CONCLUSION: Analysis of the experimental data under controlled and uncontrolled pH conditions showed that the inclusion of a correction factor for products formation, as well as a term related to the influence of H+ cations, are important for the correct modeling of this bioprocess. Compared with earlier models reported in the literature the proposed models show better fitting, with less or equal numbers of parameters, and provide parameter estimates with much lower variability. Copyright © 2011 Society of Chemical Industry

Reduced Order Models of Mistuned Cracked Bladed Disks

Predicting the influence of cracks on the dynamics of bladed disks is a very important challenge. Cracks change the structural response, which in turn changes the crack propagation characteristics. Hence, accurate and computationally effective means to model the dynamics of cracked bladed disks and blisks is particularly crucial in applications such as prognosis, guidance for repairs, characterization after repairs, design, and structural health monitoring. Most current models of bladed disks exploit cyclic symmetry to gain computational efficiency. However, the presence of cracks and mistuning destroys that symmetry and makes computational predictions much more expensive. In this work, we propose a new reduced order modeling methodology that can speed up computations by several orders of magnitude. There are two key components of the new methodology. First, the displacements and deformations of the crack surfaces are not modeled in absolute coordinates but relative coordinates, which allows for an effective model reduction based on (fixed-interface Craig–Bampton) component mode synthesis (CMS). The use of relative coordinates allows one to define one of the components in CMS as the pristine/uncracked structure (with mistuning). This approach is used in combination with a set of accurate approximations for the constraint modes used in CMS. Second, the effects of mistuning are captured by component mode mistuning, which allows the construction of extremely efficient reduced order models for the pristine/uncracked component with mistuning. The novel proposed method is applied to a finite element model of an industrial blisk. The combined presence of mistuning and cracks is shown to have important effects. Also, the proposed approach is shown to provide accurate predictions for the overall blisk while requiring computations using single-sector models only. The influence of various parameters on the accuracy of the reduced order models is investigated. Overall, the results show a very good agreement between full finite element analyses and the proposed reduced order modeling approach.

A Master Model Approach to Multidisciplinary Design and Simulation for Compressor Blisk

Multidisciplinary design and simulation is a very effective process to balance the different discipline design requirements and gain the optimal design result. The paper proposes a master model approach in order to maintain the model associativity and consistency in multidisciplinary design and simulation for compressor blisk. The research presents a master model-centered model structure, which is composed of master model, context model and application model. In the proposed master model-based multidisciplinary design and simulation process, master model is the kernel model and shared by each discipline. In addition, there is an associative relationship among these models. Then, the paper studies the modeling method for the master model of blisk and the model mapping and associativity maintaining method for multidisciplinary design and simulation. A series of computation results demonstrate the performance of the proposed approach.

Control of the electromagnetic compatibility: An issue for IC reliability

This paper deals with the use of two main standard modeling approaches in order to control the electromagnetic compatibility of an IC before manufacturing. An application is given in the case of a complex mixed circuit which is an Analog to Digital Converter (ADC) embedded in a microcontroller. The digital core (DC) of the microcontroller consumes dynamic currents which generate internal disturbances and, as a consequence, a loss of the ADC accuracy is observed. At first, the conducted emission of the DC is estimated by using the ICEM-CE model. Then, the ADC immunity is modeled with ICIM-CI methodology. Based on these two models, a simulation at the chip level is performed to estimate the loss of accuracy of this ADC. Finally, this study is the first step in the development of a methodology for virtual prototyping allowing, from the design, the evaluation of the integrated circuit sensitivity to electromagnetic interference in order to improve its reliability.

Special Issue: Sustainable Development of Energy, Water and Environment Systems

The 5th Dubrovnik Conference on Sustainable Development of Energy, Water and Environment Systems (held in 2009) was attended by 307 scientists from 55 countries and 6 continents. The majority of the participants focused on methods, policies and technologies for increasing the sustainability of development, while always considering the economic, environmental and social aspects involved. With special reference to water science, the presented articles considered the link of both pillars of the conference (i.e. water and energy) all under the prism of environmental sustainability. The selected papers mainly discuss state-of-the-art water resources management issues which refer to applied international approaches and policies. Among others, they discuss water resources management issues in the framework of the European Water Framework Directive (WFD) 2000/60/EC, advanced technologies in the field of wastewater treatment (WWT) as well as engineering water works for water storage techniques and methodologies. Water Framework Directive 2000/60/EC is considered as one of the most important legislative enactments -within the context of European environmental law and policywith respect to the management and protection of water resources within the European region. Bilaletdin et al., use steady state and dynamic modeling approach in order to assess the impacts of different loading scenarios of water quality of Lake Onega, the second largest lake in Europe, as demanded by the WFD. Martinez et al., assuming that the physical laws are called to be the objective and universal tools to assess water costs, developed Physical Hydronomics (PH) as the accounting tool for the WFD application, regarding its physicochemical objectives. Water Resour Manage (2011) 25:2917–2918 DOI 10.1007/s11269-011-9888-9

Network Modeling of MDM2 Inhibitor-Oxaliplatin Combination Reveals Biological Synergy in wt-p53 solid tumors

Earlier we had shown that the MDM2 inhibitor (MI-219) belonging to the spiro-oxindole family can synergistically enhance the efficacy of platinum chemotherapeutics leading to 50% tumor free survival in a genetically complex pancreatic ductaladenocarcinoma (PDAC) xenograft model. In this report, we have taken a systems and network modeling approach in order to understand central mechanisms behind MI219-oxaliplatin synergy with validation in PDAC, colon and breast cancer cell lines. Microarray profiling of drug treatments (MI-219, oxaliplatin or their combination) in capan-2 cells reveal a similar unique set of gene alterations that is duplicated in other solid tumor cells. As single agent, MI-219 or oxaliplatin induced alterations in 48 and 761 genes respectively. The combination treatment resulted in 767 gene alterations with emergence of 286 synergy unique genes. Ingenuity network modeling of combination and synergy unique genes showed the crucial role of five key local networks CREB, CARF, EGR1, NF-kB and E-Cadherin. Compared to single agents the combination treatment super induced p53 and p21 confirming functional synergy. Further, the network signatures were validated at the protein level in all three cell lines. Individually silencing central nodes in these five hubsinterfered with MI-219-oxaliplatin activity confirming their critical role in aiding p53 mediated apoptotic response. We anticipate that our MI219-oxaliplatin network blueprints can be clinically translated in the rationale design and application of this unique therapeutic combination in a genetically pre-defined subset of patients.

A General Water Protection Plan of Lake Onega in Russia

Lake Onega is the second largest lake in Europe after Lake Ladoga. This paper is a part of the project concerning a general plan of water protection, as expressed in the Water Framework Directive. The aim of this paper was to present an investigation of the status of Lake Onega and to present steady state and dynamic modelling approach in order to assess the impacts of different loading scenarios of water quality of Lake Onega. In the project more catchment and water quality models were used but in this paper these models were chosen. The presented steady state model was the mass balance model of Vollenweider and the dynamic model is the box-type model AQUATOX. While Lake Onega preserves a good status of water as a whole, the problems with pollution and eutrophication exist in Petrozavodsk and Kondopoga Bays where anthropogenic loading is more pronounced.

Modeling the Long Term Fate of Oil-Mineral-Aggregates (OMAs) in the Marine Environment and Assessment of Their Potential Risks

ABSTRACT Spilled oil can interact with suspended particles (mineral or organic) in marine environments and form aggregates, including oil-mineral-aggregates (OMAs). Some OMAs with densities greater than seawater can settle to the seedbed and pose potential risks to benthic organisms. To understand the transport and fate of oil associated with OMAs and evaluate their potential risks, researchers recently developed an integrated hydrodynamic, fate/transport and risk assessment modeling system, and conducted several case studies. One of the limitations of these studies was the use of a conservative approach which neglected biodegradation processes. Although this approach is acceptable for the study of short term effects of settled oil, the long term effects cannot be studied. It is the objective of this paper to improve the existing modeling approach in order to simulate the long term fate/transport and potential risk of settled oil associated with OMAs. The improved approach used the DREAM model developed b...