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Search Results: 1 - 10 of 7048 matches for " modeling "
All listed articles are free for downloading (OA Articles)
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Effectively Using the QRFM to Model Truck Trips in Medium-Sized Urban Communities  [PDF]
Michael D. Anderson, Mary C. Dondapati, Gregory A. Harris
Journal of Transportation Technologies (JTTs) , 2013, DOI: 10.4236/jtts.2013.33018
Abstract: This paper analyses the effectiveness of applying the Quick Response Freight Manual (QRFM) to model freight transportation. Typically, freight transportation is indirectly modeled or as an after-thought. Increasing freight volumes, coupled with cost saving strategies such as just-in-time delivery systems, require that transportation policymakers analyze infrastructure needs and make investment decisions that explicitly include freight volumes as a component. This paper contains a case study using a medium sized urban area travel model and the QRFM trip generation and a distribution methodology to provide a framework for freight planning that can be used to improve resource allocation decisions.
Modeling Population Growth: Exponential and Hyperbolic Modeling  [PDF]
Dean Hathout
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.42045
Abstract:

A standard part of the calculus curriculum is learning exponential growth models. This paper, designed to serve as a teaching aid, extends the standard modeling by showing that simple exponential models, relying on two points to fit parameters do not do a good job in modeling population data of the distant past. Moreover, they provide a constant doubling time. Therefore, the student is introduced to hyperbolic modeling, and it is demonstrated that with only two population data points, an amazing amount of information can be obtained, such as reasonably accurate doubling times that are a function of t, as well as accurate estimates of such entertaining topics as the total number of people that have ever lived on earth.

An Example of an Investment Model That Makes Something Out of Nothing (Sort of): Implications for Building Applied Mathematical Models  [PDF]
Greg Samsa
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.48A012
Abstract:

Two related and under-studied components of modeling are: a) the process by which simplifying assumptions are derived; and b) the process by which tests of model validity are designed. This case study illustrates these processes for two simple investment models: a) a version of the model supporting classical portfolio theory; and b) a version of a mean-reverting model consistent with some of the tenets of behavioral finance. We perform a simulation that demonstrates that the traditional method of empirically assessing the performance of value investment strategies is underpowered. Indeed, the simulation illustrates in a narrow technical sense how to make something out of nothing; namely, how to generate increased returns while reducing risk. Analyzing the mechanism underpinning this counter-intuitive result helps to illustrate the close and sometimes unexpected relationship between the substantial assumptions made about the systems being modeled, the mathematical assumptions used to build models of those systems, and the structure of the experiments used to assess the performance of those models.

Video Frame’s Background Modeling: Reviewing the Techniques  [PDF]
Hamid Hassanpour, Mehdi Sedighi, Ali Reza Manashty
Journal of Signal and Information Processing (JSIP) , 2011, DOI: 10.4236/jsip.2011.22010
Abstract: Background modeling is a technique for extracting moving objects in video frames. This technique can be used in ma-chine vision applications, such as video frame compression and monitoring. To model the background in video frames, initially, a model of scene background is constructed, then the current frame is subtracted from the background. Even-tually, the difference determines the moving objects. This paper evaluates a number of existing background modeling techniques in term of accuracy, speed and memory requirement.
Control of Leaf Spot Diseases on Ecotypes of Faba Bean (Vicia faba L.) Produced in the Andean Region of Bolivia  [PDF]
M. Coca-Morante, F. Mamani-álvarez
American Journal of Plant Sciences (AJPS) , 2012, DOI: 10.4236/ajps.2012.38139
Abstract: The basin of Lake Titicaca is a faba bean-producing microregion of Bolivia where the crop is destined for export. The most commonly cultivated ecotypes “Gigante de Copacabana” and “Usnayo” are affected by diseases that can cause production losses. The aims of the present work were to identify the causal agents of leaf spot affecting these ecotypes, to record disease intensity levels, and to estimate their effect on production. In 2004 and 2005, leaflet, stem and pod samples were taken from faba bean plants with leaf spot growing in the Lake Titicaca area, and from plants in an experimental plot established to determine the effect of five different treatments on production and disease intensity: T1 = Control; T2 = seed treatment with Trichoderma sp. + alternate foliar spraying with benomyl and mancozeb; T3 = seed treatment with fludioxanil/metalaxyl M + alternate foliar spraying with benomyl and mancozeb; T4 = foliar spraying with Trichoderma sp.; T5 = alternate foliar spraying with cymoxanyl and mancozeb-chlorothalonil. Microscopic analysis of the samples revealed the presence of new fungal pathogens for faba beans in Bolivia (Cladosporium sp., and Lepthosphaerulina sp.) as well as emerging fungal pathogens (Botrytis cinerea, B. fabae, Ascochyta fabae, Alternaria sp. and Cercospora sp.). None of the treatments affected the disease progression curve (DPC) for incidence, although effects were seen with respect to disease severity. The seed + foliar treatments (T2 and T3) were more effective at controlling disease than leaf treatments on their own (T4 and T5). Modelling analysis showed faba bean leaf spot disease to be moderately destructive. Compared to chemical treatments, biocontrol with Trichoderma spp. preliminary was found to provide good control of the disease. Losses due to leaf spot disease of 36% were recorded, and a strong correlation detected between yield and disease severity.
Modeling Fiber Composites during the Cure Process for Piezoelectric Actuation  [PDF]
Darryl V. Murray, Oliver J. Myers
World Journal of Mechanics (WJM) , 2013, DOI: 10.4236/wjm.2013.31002
Abstract:

Analytical, numerical, and experimental modeling methods are presented to predict deformation after the cure process of thin unsymmetric laminates for piezoelectric actuation. During fabrication, laminates deform to several post-cure room temperature shapes. Thin cross-ply laminates deform to a circular cylindrical post-cure shape while thicker laminates deform to a saddle shape. Post-cure shapes are dependent on ply orientation, thickness, and material properties. Because, CLT alone does not always predict the correct post-cure room temperature shape of the thin composite laminates, an extension of CLT with the Rayleigh-Ritz technique and potential energies are used to better predict these shapes. Finite element models are used to predict the post-cure room temperature shapes. Thin composite laminates are modeled coupling heat transfer and structural mechanics, which are necessary for modeling the cure process. Modeling the fabrication process captured important data such as residual stresses from the cure process, room temperature shapes, and bi-stability of the composite laminates. To validate these analytical and numerical results, experiments were con- ducted using macro-fiber composite (MFC) patches for morphing the laminates. The experimental piezoelectric morph- ing results relate well to analytical and numerical results.

A mathematical perspective on the determination of coastal peopling nuclei  [PDF]
Claude Gauthier, Ahcène Brahmi, Ghislain Vautour
Natural Science (NS) , 2013, DOI: 10.4236/ns.2013.51003
Abstract: Two versions of a mathematical model are proposed for the process underlying the choice of settlement sites of past, present and future populations along the world coastline. The model is primarily based on the geometry of coastline at the scale of the map representing the region under study. It can be used to determine sites of human occupation for archaeological interest, as well as to plan future movements of present coastal populations due to the current sea level rise. Two examples related to history are presented: the first applies to the coastal peopling of the Mediterranean region, and the second to the settlement of Acadians in North-East of the Canadian province of New Brunswick in the second half of the 18th century.
A novel algorithm for describing population level trends in body weight  [PDF]
Azadeh Alimadad, Carrie Matteson, Warren L. Hare, Ozge Karanfil, Diane T. Finegood
Health (Health) , 2012, DOI: 10.4236/health.2012.412A217
Abstract:

Modeling population trends and predicting the impact of interventions to address obesity requires algorithms for predicting body weight status in the future. Predictions can be based on statistical consideration of different risk factors, or be an extrapolation of past and current trends. Despite the well known correlation between previous and future weight, individual weight history has not been used to predict future trends. We developed a novel population-level model to examine trends of different classes of body weight considering individual body weight histories from the National Longitudinal Survey of Youth (NLSY79). A subset of data used to assess the predictive ability of our proposed model with actual data. Our results confirm the importance of weight history in determining future weight status. Over 80% of individuals in a specific weight category (normal, overweight, obese) will stay in the same weight category after two years (except overweight females). The length of body weight stability was also found to be important. The probability of remaining normal weight increased with longer prior periods of being at a normal weight over 18 years (0.834 to 0.893). We demonstrate that an individual’s most probable weight class in the future is consistent with their maximal historical weight class.

A Survey of Modeling and Control of Piezoelectric Actuators  [PDF]
Jingyang Peng, Xiongbiao Chen
Modern Mechanical Engineering (MME) , 2013, DOI: 10.4236/mme.2013.31001
Abstract:

Piezoelectric actuators (PEAs) have been widely used in micro- and nanopositioning applications due to their fine resolution, fast responses, and large actuating forces. However, the existence of nonlinearities such as hysteresis makes modeling and control of PEAs challenging. This paper reviews the recent achievements in modeling and control of piezoelectric actuators. Specifically, various methods for modeling linear and nonlinear behaviors of PEAs, including vibration dynamics, hysteresis, and creep, are examined; and the issues involved are identified. In the control of PEAs as applied to positioning, a review of various control schemes of both model-based and non-model-based is presented along with their limitations. The challenges associated with the control problem are also discussed. This paper is concluded with the emerging issues identified in modeling and control of PEAs for future research.

 

An Automated Model for Fitting a Hemi-Ellipsoid and Calculating Eigenvalues Using Matrices  [PDF]
Alicia R. Billington, Peter J. Fabri, William E. Lee III
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.52025
Abstract:

Ellipsoid modeling is essential in a variety of fields, ranging from astronomy to medicine. Many response surfaces can be approximated by a hemi-ellipsoid, allowing estimation of shape, magnitude, and orientation via orthogonal vectors. If the shape of the ellipsoid under investigation changes over time, serial estimates of the orthogonal vectors allow time-sequence mapping of these complex response surfaces. We have developed a quantitative, analytic method that evaluates the dynamic changes of a hemi-ellipsoid over time that takes data points from a surface and transforms the data using a kernel function to matrix form. A least square analysis minimizes the difference between actual and calculated values and constructs the corresponding eigenvectors. With this method, it is possible to quantify the shape of a dynamic hemi-ellipsoid over time. Potential applications include modeling pressure surfaces in a variety of applications including medical.

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