Comparative study of metamodeling and sampling design for expensive and semi-expensive simulation models under uncertainty

In spite of the wide improvements in computer simulation packages, many complex simulation models, particularly under uncertainty, may be inefficient to run in terms of time, computation, and resources. To address such a challenge, integrating metamodels and robust design optimization has been applied. In the current paper, a systematic comparative study is implemented to evaluate the performance of three common metamodels, namely polynomial regression, kriging, and radial basis function. The required experiments are designed by different space-filling methods including the orthogonal array design and three forms of Latin hypercube sampling such as randomized, maximin, and correlation approaches. Although, the impact of sample size on the performance of metamodels in robust optimization results are investigated. All methods are analyzed using five two-dimensional test problems and one engineering problem while all of them are considered in two forms that are expensive (with a small sample size) and semi-expensive (with a large sample size). Uncertainty is assumed in all problems as a source of variability, so all test problems are conducted in the format of robust optimization in the class of dual response surface in order to estimate robust Pareto frontier. The performances of methods are studied in two terms of accuracy and robustness. Finally, the results of comparison, an applicable guideline is provided to aid the practitioners in selecting the appropriate combination of metamodels and sampling design methods for investigating set of robust optimal points (estimated Pareto frontier) in simulation–optimization problems under uncertainty. </jats:p

CFD modelling of weld pool formation and solidification in a laser micro-welding process

202402 bcchAccepted ManuscriptOthersUniversity of Malaya Postgraduate Research GrantPublishedGreen (AAM

Development of cantaloupe (Cucumis melo) juice powders using spray drying technology

Cantaloupes are a good source of carotenoids and vitamin C. Cantaloupe fruit juice powder containing vitamin C and β-carotene can be produced by spray drying. The objective of this study was to develop cantaloupe fruit juice (CJ) powder and to evaluate its nutritional and physical properties. Fresh cantaloupe fruits purchased from a local store were diced and juiced. CJ with 10% maltodextrin (MD) added was spray dried at inlet temperatures of 170, 180 and. /or 190 °C. Three spray dried cantaloupe powders, including CJ dried with MD at 170 °C (CJP1), CJ dried with MD at 180 °C (CJP2), CJ dried with MD at 190 °C (CJP3) were analyzed for moisture, water activity, vitamin C, β-carotene, dissolution, and microstructure. The actual production rate of the cantaloupe juice powders was lower than the estimated production rate. CJP1 had (p \u3c 0.05) higher moisture content and water activity than CJP2, and CJP3. Vitamin C content (mg/100 g, dry solids) was significantly (p \u3c 0.05) higher in CJP1 (136.36 ± 5.84) than CJP2 (91.85 ± 5.23) and CJP3 (78.30 ± 1.96). The powder produced at inlet temperatures 170 °C had higher β-carotene content (μg/g) than that produced at 180 and 190 °C. © 2011 Elsevier Ltd

Involvement and interactions of different immune cells and their cytokines in human visceral leishmaniasis

Visceral leishmaniasis (VL) or kala-azar, a disseminated infection of the lymphoreticular system of the body, is marked by severe defect in immune system of the host. Successful cure of VL depends on the immune status of the host in combination with the effects of the antileishmanial drugs. The rationale approach towards eradication of this disease would be to potentiate the immune functioning of the host in addition to parasite killing. This review deals with different aspects of adaptive and innate immune responses and explores their role in protection or pathogenesis of VL. IL-10 has emerged as the principal cytokine responsible for disease pathogenesis, although evidences regarding its source during active VL remain inconclusive. On the other hand, IFNγ, under the influence of IL-12, is mostly correlated with healing of the disease. Chemokines are important in mounting cell-mediated immune response as they can prevent parasite invasion in association with cytokines. Different types of T cells like CD4, CD8 and NK T cells also contribute to the immunology of this disease. In spite of conflicting reports, the role of regulatory T cells in VL pathogenesis is important. Recently discovered Th17 subset and its different members have been reported to perform diverse functions in the course of VL and leishmaniasis as a whole. Innate immune responses, depending on the cell types, are essential in early parasite detection and subsequent development of an efficient NK cell response. Immunotherapy targeting IL-10 could be looked upon as an interesting option for the treatment of V