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New Mathematical Model (new + mathematical_model)

Distribution by Scientific Domains
Engineering40%
Chemistry40%

Selected Abstracts

Exploring time-dependent symptom outcomes in office staff

HUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 3 2009
Xiaoshu Lu
This article illustrates the application of a new mathematical model developed for the study of time-dependent health outcomes for office staff during computer work. The model describes the time-dependent associations of computer usage with outcomes expressed as discomfort in multiple body regions. The association is explicitly presented with a functional relationship that is parameterized by body regions. The validation of the model demonstrated accuracy in reproducing the observed quantities for the study population. Therefore, we used this model to assess the impact of computer-related work exposure on discomfort in different body regions among office staff to better understand the behavior of musculoskeletal and other symptoms. The exposures and outcomes were recorded parallel in time as usage of keyboard and mouse and with diaries of discomfort. The body regions of neck/shoulders, eyes, head, shoulder joint/upper arm, and upper back were identified to have the highest discomfort levels and rates for the development of discomfort parallel with exposures. Most of our findings are consistent with the literature. The developed mathematical methodology may be used to understand how the human body reacts to computer work to further prevent potential musculoskeletal and other disorders. © 2009 Wiley Periodicals, Inc. [source]

3D computer simulation of melt flow and heat transfer in the lost foam casting process

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2003
S. M. H. Mirbagheri
Abstract A new mathematical model has been developed to simulate mould filling in the lost foam casting process, using the finite difference method. The simulation of molten flow and track of free surfaces is based on the SOLA-VOF numerical technique. An algorithm was developed to calculate the gas pressure of the evaporated foam during the mould filling. The effect of backpressure on the filling behaviour was modelled with an experimental function by adding three-dimensions 3DVOF functions. In order to verify the computational results, a thin grey iron plate was poured into a transparent mould. Cavity filling, foam depolymerization and gap formation were recorded with a 16mm high-speed camera. A good agreement was achieved for simulation results of filling sequences with those from experiments. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Mathematical modeling of gas-phase biofilter performance

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2003
Hasnaa Jorio
Abstract In the present paper, a new mathematical model describing the physical, chemical and biological phenomena involved in the process of contaminant removal in biofilters is developed. In addition to the contaminant, the key components of the present theoretical model are carbon dioxide and oxygen. The model predicts the concentration profile of the key components in the gas phase, the biofilm and the sorption liquid retained in the solid particles composing the filter bed at both steady and transient regimes. The model equations were solved numerically and comparison between theory and experiment showed that the model results for styrene and carbon dioxide concentration profiles were in very good agreement with experimental data for the biofiltration of styrene vapors at steady state. The analysis of oxygen concentration profile in the biofilm predicted by the theoretical model revealed that oxygen limitation does not occur under the operating styrene biodegradation rate in the biofilter. Copyright © 2003 Society of Chemical Industry [source]

Models of influence in chronic liver disease

LIVER INTERNATIONAL, Issue 5 2010
Amnon Sonnenberg
Abstract Background & Aims: Liver disease is often characterized by an intricate network of multiple, simultaneously interacting factors with organ-specific, as well as systemic effects. The aim of the present study is to introduce a new mathematical model on how to weigh a variety of factors contributing to chronic liver disease by the relevance of their influence on the overall disease processes. Methods: Liver disease is modelled as the interaction of multiple internal and external factors. Each factor can potentially interact with any of the other factors in the model. The strength of interactions is expressed as per cent. The sum of all interactions contributing to each individual factor adds up to 100%. This model corresponds mathematically to a transposed Markov matrix. The analysis uses the two examples of hepatitis C virus (HCV) and autoimmune hepatitis (AIH). Results: Impaired liver function is the most influential factor and increases in relevance as the degree of hepatic fibrosis increases. The relative importance of treating the primary disease process (HCV or AIH) diminishes as fibrosis develops. Similarly, psychosocial factors become less important with disease progression. Liver transplant is most important for Child's C cirrhosis. It is relatively influential for the early phase of AIH but not HCV, reflecting the fact that some cases of non-cirrhotic AIH can progress rapidly to acute liver failure. Conclusion: In a disease process characterized by a large array of multiple interacting factors, the decision tool of a transposed Markov chain helps to sort the contributing factors by the magnitude of their influence. [source]

Improvement of inter-instrumental agreement for reflectance spectrophotometers

COLORATION TECHNOLOGY, Issue 6 2004
Y S Chung
The repeatability and inter-instrumental agreement of reflectance spectrophotometers have been investigated in this study. Both glossy and matt types of standard tiles were used and it was found that the different spectrophotometers differed considerably with one another. A new mathematical model for inter-instrumental agreement (the R-model) was developed. The improvement of the inter-instrumental agreement after applying the model was 82,90% with the appropriate measurement settings. The concept of using an instrumental profile for a spectrophotometer against a reference instrument was tested and the results of the inter-instrumental agreement after applying the profiles also showed significant improvement. The performance of the R-model was compared with the two previously published models and the results showed that the R-model outperformed the other two models based on the measurements of both standard tiles and textile samples. [source]