Key Design Variables Research Articles

Support vector regression models for trickle bed reactors

Transport phenomena in multiphase reactors are poorly understood and first-principles modeling approaches have hitherto met with limited success. Industry continues thus far to depend heavily on engineering correlations for variables like pressure drop, transport coefficients and wetting efficiencies. While immensely useful, engineering correlations typically have wide variations in their predictive capability when venturing outside their instructed domain, and hence universally applicable correlations are rare. In this contribution, we present a machine learning approach for modeling such multiphase systems, specifically using the Support Vector Regression (SVR) algorithm. An application of trickle bed reactors is considered wherein key design variables for which numerous correlations exist in the literature (with a large variation in their predictions), are all correlated using the SVR approach with remarkable accuracy of prediction for all the different literature data sets with wide-ranging databanks.

Influencing Factors of Contact Force Distribution in Pedestrian Upper Legform Impact with Vehicle Front-End

Pedestrian upper leg impact protection is a challenging requirement in the Euro NCAP assessment. In upper legform to bonnet leading edge tests, the legform impact force, the legform intrusion and the injury parameters (impact force and bending moment measured on the upper legform) are highly related to design of vehicle front-end styling and structure, as well as clearance underneath bonnet leading edge. In the course of impact, the contact area variation has significant influence on the stress distribution and consequently the force and the bending moment on the upper legform. Using finite element simulations of upper legform impact with a typical sedan, the deformation of the legform and the vehicle structure, and the variation of the contact force distribution are characterized and analyzed. Based on the study, a method for calculating the contact force is put forward by assuming a shape of the contact zone on the upper legform and a stress distribution function within the contact zone. The calculation method is verified using a simplified model of vehicle front-end structure developed in a previous study. Then a parametric study is conducted using the simplified vehicle front-end model to study influence of key design variables. The results of the parametric study, to some extent, have revealed relationship among vehicle front-end design parameters such as styling, geometry and stiffness, contact characteristics such as the maximum stress on outer foam, and the injury parameters (mainly the impact force). Language: en

Wheel Loader Working Device Optimization Design Based on the Sensitivity Analysis

As designing the loader working device related to multi-variables, multi-objective and it is a non-linear constrained complex optimization problem essentially so using traditional optimization method to design the loader working device is low efficiency. A new method is proposed which combines the sensitivity analysis with the genetic algorithms to reduce the design variables and to improve the optimization efficiency. The optimization mathematical model is established. The key design variables which have greater impact on the loader digging force can be obtained by the sensitivity analysis and then input into genetic algorithms to conduct an optimization. By using this method the result showed that the loader digging force can be increased by 5.9 percent on the premise of meeting the overall performance requirements of the loader.

The use of quasi-static testing to obtain the low-velocity impact damage resistance of marine GRP laminates

The use of more economical quasi-static testing to predict the dynamic impact behaviour of marine GRP composites has been evaluated by comparing equivalent impact and quasi-static test results. Static tests predicted well the initial impact behaviour and onset of delamination damage, which is likely to be the key impact resistance design variable. However, only very conservative estimates of the final fibre failure and total energy absorption capacity were achieved, except for the thickest specimens where fibre damage occurred at similar loads for both static and impact tests. Quasi-static testing avoided the problems associated with oscillations in the force signal, and delamination force showed a very strong linear relationship with laminate thickness3/2 as predicted by two simplified models. It was inferred that the undamaged and delaminated responses are not strain rate dependant, but that the fibre failure mechanisms are.

Small and medium enterprises web page design: a qualitative study

The present paper is based on the results of seven consumer focus groups developed in Spain. The results are interpreted using an ethnographic summary of each focus group (qualitative approach) and a systematic coding procedure (quantitative approach). The research pursued two major objectives. Firstly, to identify the key design variables for building a successful transactional small and medium enterprises (SME) website. Secondly, the transactional relevance of each key design variable was tested in order to establish priorities according to Spanish online buyers’ preferences. The findings indicate that a SME transactional website should have three main strong points: 1 it must be secure 2 price information should be provided 3 a wide range of images should be shown. But not all these factor are equally important. The focus group methodology is presented as an extremely economic and useful technique in providing a better understanding of successful website design. This methodology underlines the need to build websites which meet consumer needs.

Closed-Form Correlation of Buildings Energy Use With Key Design Parameters Calibrated Using a Genetic Algorithm

This work aims at developing a closed-form correlation between key building design variables and its energy use. The results can be utilized during the initial design stages to assess the different building shapes and designs according to their expected energy use. Prototypical, 20-floor office buildings were used. The relative compactness, footprint area, projection factor, and window-to-wall ratio were changed and the resulting buildings performances were simulated. In total, 729 different office buildings were developed and simulated in order to provide the training cases for optimizing the correlation’s coefficients. Simulations were done using the VisualDOE TM software with a Typical Meteorological Year data file, Kuwait City, Kuwait. A real-coded genetic algorithm (GA) was used to optimize the coefficients of a proposed function that relates the energy use of a building to its four key parameters. The figure of merit was the difference in the ratio of the annual energy use of a building normalized by that of a reference building. The objective was to minimize the difference between the simulated results and the four-variable function trying to predict them. Results show that the real-coded GA was able to come up with a function that estimates the thermal performance of a proposed design with an accuracy of around 96%, based on the number of buildings tested. The goodness of fit, roughly represented by R2, ranged from 0.950 to 0.994. In terms of the effects of the various parameters, the area was found to have the smallest role among the design parameters. It was also found that the accuracy of the function suffers the most when high window-to-wall ratios are combined with low projection factors. In such cases, the energy use develops a potential optimum compactness. The proposed function (and methodology) will be a great tool for designers to inexpensively explore a wide range of alternatives and assess them in terms of their energy use efficiency. It will also be of great use to municipality officials and building codes authors.

Design and low energy ventilation solutions for atria in the tropics

a b s t r a c t A generic atrium building was designed to incorporate low energy solutions and features of both vernac- ular and contemporary South Asian architecture. To achieve low energy and comfort within the atrium space, some key design variables were examined by running a dynamic thermal model (DTM) for some representative cases. This DTM model was developed with multiple levels and zones to simulate the heat and air movement throughout the building and validated with the data measured in a real building of similar form. The modelling study was carried out to investigate the effects of two roof forms for the atrium and three low cost ventilation solutions on indoor thermal comfort. It reveals that low cost ven- tilation and acceptable comfort are achievable in this traditional form of architecture and low energy solutions and careful design can complement well its functional aspects and even enhance its aesthetic and practical qualities. The solar heat gain, air temperature, and mean radiant temperature in the atrium were used to assess the effectiveness of clerestory windows with opaque rooftop (i.e. side-lit model) as compared to the fully transparent glazed rooftop (i.e. top-lit model). Data on cooling loads, indoor air temperature, and mean radiant temperature were used to evaluate the design options with special consideration on local adaptable thermal comfort criteria. The possible effects of the research outcomes on the incorporation of atria are discussed at the end.

Researches on Modeling and Simulation of Continuous Wave Mud Pulser

Computer simulation of flow fields about “mud pulser” used in Drilling are studied using a dynamic formulation that models the effects of key design variables on rotor torque. Well known field problems are reviewed and aerodynamically based solutions are explained in detail. The solution of problem is studied numerically and the computer model show replicate the main physical features. The simulation focuses on techniques that ensure fast stable rotary movements for supporting fast transmissions of future drilling and logging working.

Successful SME web design through consumer focus groups

Purpose – The purpose of this research is to pursue two major objectives. First, to identify the key design variables for building successful transactional SME (Small Medium Enterprises) websites. Second, the transactional relevance of each key design variable is tested in order to establish priorities.Design/methodology/approach – The present paper is developed through seven consumer focus groups. Two approaches were used: an ethnographic summary of each focus group (qualitative approach) and a systematic coding procedure (quantitative approach).Findings – The findings indicate that a transactional website should have three main strong points: it must be secure; price information should be provided; and a wide range of images should be shown. But not all these factors are equally important.Practical implications – These results lead one to recommend that managers should expend more effort to make the website more secure and detailed in terms of content. Second, even e‐services have not obtained the highe...

Optimization of the head shape of the CRH3 high speed train

Aiming at optimizing the head shape of the CRH3 high speed train, an efficient optimization approach is proposed. The CFD analysis by solving Navier-Stokes equations is coupled with optimization calculation based on the multi-objective genetic algorithm, meanwhile the arbitrary shape deformation technique (ASD) is also introduced into the design flow, which greatly shortens the time consumption for geometry regeneration and flow field remeshing. As a result, the efficiency of the optimization calculation is highly improved. Statistical analysis is done to the designs in the design space, and the correlation between the design variables and the objective is studied to find out the key variables that most affect the objective. Response surface analysis is also performed to get the nonlinear relationship between the key design variables and the objective with the Kriging algorithm. Finally, after the optimization, an aerodynamic performance comparison between the optimal shape and the original shape reveals that the original shape of CRH3 high speed train owns a very stable aerodynamic performance and can be trustingly used in industry.

Towards optimal design of high‐rise building tube systems

AbstractThe primary objectives of this study are to investigate effects of varying design parameters on the tube action and shear lag behaviour of a typical reinforced concrete frame‐wall tube building, and propose optimal design approaches for similar tube structures. A parametric study was conducted with selected key design variables on the performance of a 55‐storey hotel building planned in New York City. The lateral force resistance of the case study building is primarily exerted by exterior shear walls in one direction and by exterior moment frames in the other direction, enhanced by the tube action credited to the connection of the walls and the frames. The design variables considered for the parametric study include the column depth, beam depth, column width and beam width of the moment frames. The performance of each model was assessed in terms of overall and critical (maximum) storey drifts, force distributions between various lateral force‐resisting members and shear lag behaviour. Overall, the effects of the column depth (column dimension parallel to the frame direction) on the tube action and shear lag behaviour were more prominent than the other member dimensions. Copyright © 2010 John Wiley & Sons, Ltd.

Multiple regression models for energy use in air-conditioned office buildings in different climates

An attempt was made to develop multiple regression models for office buildings in the five major climates in China – severe cold, cold, hot summer and cold winter, mild, and hot summer and warm winter. A total of 12 key building design variables were identified through parametric and sensitivity analysis, and considered as inputs in the regression models. The coefficient of determination R 2 varies from 0.89 in Harbin to 0.97 in Kunming, indicating that 89–97% of the variations in annual building energy use can be explained by the changes in the 12 parameters. A pseudo-random number generator based on three simple multiplicative congruential generators was employed to generate random designs for evaluation of the regression models. The difference between regression-predicted and DOE-simulated annual building energy use are largely within 10%. It is envisaged that the regression models developed can be used to estimate the likely energy savings/penalty during the initial design stage when different building schemes and design concepts are being considered.

Analogs Supporting Design of Lunar Command, Control, Communication, and Information Architectures

This paper demonstrates how a survey of carefully selected analogs can be employed to map the multi-dimensional trade space for the design of information exchange oriented services in a system-of-systems context. Pursuant to this idea, a survey was conducted across historicalandcontemporaryanalogsforcrewedandroboticlunarsurfaceoperationmissions. Survey results were used to generate a list of key design variables and options available for the design of Lunar Command, Control, Communication, and Information architectures for such missions. Organization of these variables and options yielded a broad design trade space. However, some portion of the trade space covered design considerations not presented in the analogs; these unique considerations were characterized and added to the trade space by subject matter experts in the relevant application domains. The survey also provided insights into useful combinations of design options within the trade space as determined by successes across several analogs (even though the operational conditions were varied).As an overarching result, combining the system-of-systems trade space and insights extracted from the analog survey with those of application problem specific design experts is shown to be most effective method for formulating prospective architectural design solutions for further investigation via model-based engineering or in-field testing.

Energy and exergy efficiency comparison of horizontal and vertical axis wind turbines

In this paper, an energy and exergy analysis is performed on four different wind power systems, including both horizontal and vertical axis wind turbines. Significant variability in turbine designs and operating parameters are encompassed through the selection of systems. In particular, two airfoils (NACA 63(2)-215 and FX 63-137) commonly used in horizontal axis wind turbines are compared with two vertical axis wind turbines (VAWTs). A Savonius design and Zephyr VAWT benefit from operational attributes in wind conditions that are unsuitable for airfoil type designs. This paper analyzes each system with respect to both the first and second laws of thermodynamics. The aerodynamic performance of each system is numerically analyzed by computational fluid dynamics software, FLUENT. A difference in first and second law efficiencies of between 50 and 53% is predicted for the airfoil systems, whereas 44–55% differences are predicted for the VAWT systems. Key design variables are analyzed and the predicted results are discussed. The exergetic efficiency of each wind turbine is studied for different geometries, design parameters and operating conditions. It is shown that the second law provides unique insight beyond a first law analysis, thereby providing a useful design tool for wind power development.

Design Optimization for Cold Forging by an Integrated Methodology of CAD/FEM/ANN

In this paper, an integrated methodology of geometric modeling, finite element method (FEM) and artificial neural network (ANN) is proposed for design optimization of cold forging process. Forging processes with some key design variables are firstly simulated using rigid-plastic FEM so as to create training data for the ANN model. Then neural network model is used to predict for unseen data after being properly trained. Finally, some forging experiments are carried out to confirm the ANN prediction results, a good agreement is found between the predicted data and the measured results.

Shape effect on optimal geometric conditions in surface aeration systems

The performance of surface aeration systems, among other key design variables, depends upon the geometric parameters of the aeration tank. Efficient performance and scale up or scale down of the experimental results of an aeration system requires optimal geometric conditions. Optimal conditions refer to the conditions of maximum oxygen transfer rate, which assists in scaling up or down the system for commercial utilization. The present work investigates the effect of an aeration tank’s shape (unbaffled circular, baffled circular and unbaffled square) on oxygen transfer. Present results demonstrate that there is no effect of shape on the optimal geometric conditions for rotor position and rotor dimensions. This experimentation shows that circular tanks (baffled or unbaffled) do not have optimal geometric conditions for liquid transfer, whereas the square cross-section tank shows a unique geometric shape to optimize oxygen transfer.

System-Level Feasibility Assessment of Microwave Power Beaming for Small Satellites

Although wireless power transmission to fulfill Earth's energy needs has been a widely popularized application of microwave power beaming, one space application that remains relatively unexplored is power beaming between satellites. This paper provides a system-level analysis of the feasibility and limitations of microwave power beaming within a small-satellite cluster. This analysis consists of four parts using parametric models of spacecraft power as a function of 11 key design variables. In the first part, the existence of feasible designs is verified with a Monte Carlo design trade-space sweep. Next, a feasible baseline (reference) design is defined, and then sensitivity to individual variables is assessed. Finally, the design space is visualized with respect to six influential variables. Despite several optimistic assumptions, it is demonstrated that the small-satellite power-beaming design space is severely constrained. Feasible designs involve high transmission frequencies (greater than 33 GHz), large antenna diameters (greater than 0.93 m), and stringent proximity operations between satellites (within 740 m). Furthermore, full dependence of one small spacecraft on power provided by another is shown to be effectively infeasible. These results do suggest, however, that microwave power beaming may deserve consideration as an auxiliary or short-term emergency power mode for future small-satellite clusters.

On the Coupling of Designer Experience and Modularity in the Aerothermal Design of Turbomachinery

The turbomachinery aerodynamic design process is characterized both by its complexity and the reliance on designer experience for success. Complexity has led to the design being decomposed into modules; the specification of their interfaces is a key outcome of preliminary design and locks-in much of the final performance of the machine. Yet preliminary design is often heavily influenced by previous experience. While modularity makes the design tractable, it complicates the appropriate specification of the module interfaces to maximize whole-system performance: coupling of modularity and designer experience may reduce performance. This paper sets out to examine how such a deficit might occur and to quantify its cost in terms of efficiency. Two disincentives for challenging decomposition decisions are discussed. The first is where tried-and-tested engineering “rules of thumb” accord between modules: the rational engineer will find alluring a situation where each module can be specified in a way that maximizes its efficiency in isolation. The second is where there is discontinuity in modeling fidelity, and hence difficulty in accurately assessing performance exchange rates between modules. In order to both quantify and reduce the potential cost of this coupling, we have recast the design problem in such a way that what were previously module interface constraints become key system design variables. An example application of our method to the design of a generic turbofan core compression system is introduced. It is shown that nearly one percentage point of the equivalent compressor adiabatic efficiency can be saved.

A chaotic serpentine mixer efficient in the creeping flow regime: from design concept to optimization

Motivated by the three-dimensional serpentine channel (Liu et al. in J Microelectromech Syst 9:190-197, 2000), we introduce a chaotic serpentine mixer (CSM) and demonstrate a systematic way of utilizing a mapping method to find out an optimal set of design variables for the CSM. One periodic unit of the mixer has been designed to create two streamlines portraits crossing each other. As a preliminary study, flow characteristics and mixing in the original serpentine channel has been reinvestigated. The working principle of the CSM is demonstrated via a particle-tracking method. From the design principle and the flow characteristics of the CSM, we choose three key design variables with an influence on mixing. Then, simulations for all possible combinations of the variables are carried out. At proper combinations of the variables, almost global chaotic mixing is observed in the Stokes flow regime. The design windows obtained can be used to determine an optimal set of the variables to fit with a specific application.

Optimal steady-state design of reactive distillation processes using simulated annealing

In this paper, we investigate on a derivative-free optimization approach, simulated annealing (SA), for the optimization of the reactive distillation (RD) column design. Because RD systems exhibit non-monotonic behavior for key design variables, flowsheet optimization using simulator is difficult when derivative-based approach is employed. The SA-based optimization procedure gives an equally good or better design than the optimal flowsheet obtained from the sequential design approach. More importantly, this is achieved with much more efficient computing.