Investigating the CO2 laser cutting parameters of MDF wood composite material

Laser cutting of medium density fibreboard (MDF) is a complicated process and the selection of the process parameters combinations is essential to get the highest quality of the cut section. This paper presents laser cutting of MDF based on design of experiments (DOE). CO2 laser was used to cut three thicknesses 4, 6 and 9 mm of MDF panels. The process factors investigated are: laser power, cutting speed, air pressure and focal point position. In this work, cutting quality was evaluated by measuring, upper kerf width, lower kerf width, ratio between the upper kerf width to the lower kerf width, cut section roughness and the operating cost. The effect of each factor on the quality measures was determined and special graphs were drawn for this purpose. The optimal cutting combinations were presented in favours of high quality process output and in favours of low cutting cost

Evalaution and optimization of laser cutting parameters for plywood materials

Laser process parameters influence greatly the width of kerfs and quality of the cut edges. This article reports experiments on the laser plywood-cutting performance of a CW 1.5 kW CO2¬ Rofin laser, based on design of experiments (DOE). The laser was used to cut three thicknesses 3, 6 and 9 mm of plywood panels. The process factors investigated are: laser power, cutting speed, air pressure and focal point position. The aim of this work is to relate the cutting edge quality parameters namely: upper kerf (UK), lower kerf (LK), the ratio between upper to lower kerfs and the operating cost to the process parameters mentioned above. Mathematical models were developed to establish the relationship between the process parameters and the edge quality parameters, and special graphs were drawn for this purpose. Finally, a numerical optimization was performed to find out the optimal process setting at which both kerfs would lead to a ratio of about 1, and at which low cutting cost take place

Evolution Of Myrmecophytism In Western Malesian Macaranga (Euphorbiaceae)

Plants inhabited by ants (myrmecophytes) have evolved in a diversity of tropical plant lineages. Macaranga includes approximately 300 paleotropical tree species; in western Malesia there are 26 myrmecophytic species that vary in morphological specializations for ant association. The origin and diversification of myrmecophytism in Macaranga was investigated using phylogenetic analyses of morphological and nuclear ITS DNA characters and studies of character evolution. Despite low ITS variation, the combined analysis resulted in a well-supported hypothesis of relationships. Mapping myrmecophytism on all most parsimonious trees resulting from the combined analysis indicated that the trait evolved independently between two and four times and was lost between one and three times (five changes). This hypothesis was robust when tested against trees constrained to have three or fewer evolutionary transformations, although increased taxon sampling for the ITS analysis is required to confirm this. Mapping morphological traits on the phylogeny indicated that myrmecophytism was not homologous among lineages; each independent origin involved a suite of different specializations for ant-plant association. There was no evidence that myrmecophytic traits underwent sequential change through evolution; self-hollowing domatia evolved independently from ant-excavated domatia, and different food-body production types evolved in different lineages. The multiple origins of myrmecophytism in Macaranga were restricted to one small, exclusively western Malesian lineage of an otherwise large and nonmyrmecophytic genus. Although the evolution of aggregated food-body production and the formation of domatia coincided with the evolution of myrmecophytism in all cases, several morphological, ecological, and biogeographic factors appear to have facilitated and constrained this radiation of ant-plants

Health and social care service utilisation and associated expenditure among community-dwelling older adults with depressive symptoms

AIMS: Late-life depression has substantial impacts on individuals, families and society. Knowledge gaps remain in estimating the economic impacts associated with late-life depression by symptom severity, which has implications for resource prioritisation and research design (such as in modelling). This study examined the incremental health and social care expenditure of depressive symptoms by severity. METHODS: We analysed data collected from 2707 older adults aged 60 years and over in Hong Kong. The Patient Health Questionnaire-9 (PHQ-9) and the Client Service Receipt Inventory were used, respectively, to measure depressive symptoms and service utilisation as a basis for calculating care expenditure. Two-part models were used to estimate the incremental expenditure associated with symptom severity over 1 year. RESULTS: The average PHQ-9 score was 6.3 (standard deviation, s.d. = 4.0). The percentages of respondents with mild, moderate and moderately severe symptoms and non-depressed were 51.8%, 13.5%, 3.7% and 31.0%, respectively. Overall, the moderately severe group generated the largest average incremental expenditure (US$5886; 95$3849; 95% CI 2520-5177 or a 176% increase) and the moderate group (US$1843; 95$691; 95% CI 444-939), then gradually fell to negative between scores of 12 (US$- 35; 95$ -171; 95% CI - 417 to 76) and soared to positive and rebounded at the score of 23 (US$601; 95% CI -1652 to 2854). CONCLUSIONS: The association between depressive symptoms and care expenditure is stronger among older adults with mild and moderately severe symptoms. Older adults with the same symptom severity have different care utilisation and expenditure patterns. Non-psychiatric healthcare is the major cost element. These findings inform ways to optimise policy efforts to improve the financial sustainability of health and long-term care systems, including the involvement of primary care physicians and other geriatric healthcare providers in preventing and treating depression among older adults and related budgeting and accounting issues across services

Genomic insights into rapid speciation within the world’s largest tree genus Syzygium

Species radiations, despite immense phenotypic variation, can be difficult to resolve phylogenetically when genetic change poorly matches the rapidity of diversification. Genomic potential furnished by palaeopolyploidy, and relative roles for adaptation, random drift and hybridisation in the apportionment of genetic variation, remain poorly understood factors. Here, we study these aspects in a model radiation, Syzygium, the most species-rich tree genus worldwide. Genomes of 182 distinct species and 58 unidentified taxa are compared against a chromosome-level reference genome of the sea apple, Syzygium grande. We show that while Syzygium shares an ancient genome doubling event with other Myrtales, little evidence exists for recent polyploidy events. Phylogenomics confirms that Syzygium originated in Australia-New Guinea and diversified in multiple migrations, eastward to the Pacific and westward to India and Africa, in bursts of speciation visible as poorly resolved branches on phylogenies. Furthermore, some sublineages demonstrate genomic clines that recapitulate cladogenetic events, suggesting that stepwise geographic speciation, a neutral process, has been important in Syzygium diversification

CXCR4 identifies transitional bone marrow premonocytes that replenish the mature monocyte pool for peripheral responses

It is well established that Ly6C(hi) monocytes develop from common monocyte progenitors (cMoPs) and reside in the bone marrow (BM) until they are mobilized into the circulation. In our study, we found that BM Ly6C(hi) monocytes are not a homogenous population, as current data would suggest. Using computational analysis approaches to interpret multidimensional datasets, we demonstrate that BM Ly6C(hi) monocytes consist of two distinct subpopulations (CXCR4(hi) and CXCR4(lo) subpopulations) in both mice and humans. Transcriptome studies and in vivo assays revealed functional differences between the two subpopulations. Notably, the CXCR4(hi) subset proliferates and is immobilized in the BM for the replenishment of functionally mature CXCR4(lo) monocytes. We propose that the CXCR4(hi) subset represents a transitional premonocyte population, and that this sequential step of maturation from cMoPs serves to maintain a stable pool of BM monocytes. Additionally, reduced CXCR4 expression on monocytes, upon their exit into the circulation, does not reflect its diminished role in monocyte biology. Specifically, CXCR4 regulates monocyte peripheral cellular activities by governing their circadian oscillations and pulmonary margination, which contributes toward lung injury and sepsis mortality. Together, our study demonstrates the multifaceted role of CXCR4 in defining BM monocyte heterogeneity and in regulating their function in peripheral tissues

Output trajectory tracking for a switched nonlinear non-minimum phase system: The VSTOL aircraft

10.1109/CCA.2007.4389241Proceedings of the IEEE International Conference on Control Applications262-26

Combining global and local surrogate models to accelerate evolutionary optimization

In this paper, we present a novel surrogate-assisted evolutionary optimization framework for solving computationally expensive problems. The proposed framework uses computationally cheap hierarchical surrogate models constructed through online learning to replace the exact computationally expensive objective functions during evolutionary search. At the first level, the framework employs a data-parallel Gaussian process based global surrogate model to filter the evolutionary algorithm (EA) population of promising individuals. Subsequently, these potential individuals undergo a memetic search in the form of Lamarckian learning at the second level. The Lamarckian evolution involves a trust-region enabled gradient-based search strategy that employs radial basis function local surrogate models to accelerate convergence. Numerical results are presented on a series of benchmark test functions and on an aerodynamic shape design problem. The results obtained suggest that the proposed optimization framework converges to good designs on a limited computational budget. Furthermore, it is shown that the new algorithm gives significant savings in computational cost when compared to the traditional evolutionary algorithm and other surrogate assisted optimization frameworks

Observer-based fault detection for piecewise linear systems: Continuous-time cases

10.1109/CCA.2007.4389260Proceedings of the IEEE International Conference on Control Applications379-38

Observer-based fault detection for piecewise linear systems: Discrete-time cases

10.1109/CCA.2007.4389259Proceedings of the IEEE International Conference on Control Applications373-37