Surrogate Assisted Optimisation for Travelling Thief Problems

The travelling thief problem (TTP) is a multi-component optimisation problem involving two interdependent NP-hard components: the travelling salesman problem (TSP) and the knapsack problem (KP). Recent state-of-the-art TTP solvers modify the underlying TSP and KP solutions in an iterative and interleaved fashion. The TSP solution (cyclic tour) is typically changed in a deterministic way, while changes to the KP solution typically involve a random search, effectively resulting in a quasi-meandering exploration of the TTP solution space. Once a plateau is reached, the iterative search of the TTP solution space is restarted by using a new initial TSP tour. We propose to make the search more efficient through an adaptive surrogate model (based on a customised form of Support Vector Regression) that learns the characteristics of initial TSP tours that lead to good TTP solutions. The model is used to filter out non-promising initial TSP tours, in effect reducing the amount of time spent to find a good TTP solution. Experiments on a broad range of benchmark TTP instances indicate that the proposed approach filters out a considerable number of non-promising initial tours, at the cost of omitting only a small number of the best TTP solutions

Authors' reply to Colquhoun and Buchinsky

No abstract available

Advanced composite combustor structural concepts program

An analytical study was conducted to assess the feasibility of and benefits derived from the use of high temperature composite materials in aircraft turbine engine combustor liners. The study included a survey and screening of the properties of three candidate composite materials including tungsten reinforced superalloys, carbon-carbon and silicon carbide (SiC) fibers reinforcing a ceramic matrix of lithium aluminosilicate (LAS). The SiC-LAS material was selected as offering the greatest near term potential primarily on the basis of high temperature capability. A limited experimental investigation was conducted to quantify some of the more critical mechanical properties of the SiC-LAS composite having a multidirection 0/45/-45/90 deg fiber orientation favored for the combustor linear application. Rigorous cyclic thermal tests demonstrated that SiC-LAS was extremely resistant to the thermal fatigue mechanisms that usually limit the life of metallic combustor liners. A thermal design study led to the definition of a composite liner concept that incorporated film cooled SiC-LAS shingles mounted on a Hastelloy X shell. With coolant fluxes consistent with the most advanced metallic liner technology, the calculated hot surface temperatures of the shingles were within the apparent near term capability of the material. Structural analyses indicated that the stresses in the composite panels were low, primarily because of the low coefficient of expansion of the material and it was concluded that the dominant failure mode of the liner would be an as yet unidentified deterioration of the composite from prolonged exposure to high temperature. An economic study, based on a medium thrust size commercial aircraft engine, indicated that the SiC-LAS combustor liner would weigh 22.8N (11.27 lb) less and cost less to manufacture than advanced metallic liner concepts intended for use in the late 1980's

Waist-to-height ratio and cardiometabolic risk factors in adolescence: findings from a prospective birth cohort

What is already known about this subject In adults, associations between body mass index (BMI), waist-to-height ratio (WHtR) and cardiometabolic outcomes are similar. In children and adolescents, results from cross-sectional studies examining the associations between BMI z scores, WHtR and cardiometabolic outcomes are conflicting and there is a paucity of prospective data.<p></p> What this study adds This is the first study to demonstrate the prospective association between WHtR in childhood and cardiometabolic outcomes in adolescent boys. WHtR is a simple calculation that can be used to identify children and adolescents for cardiometabolic risk without the need for reference growth charts. The WHtR cut-point of ≥0.5 was highly specific in identifying cardiometabolic risk co-occurrence but has poor sensitivity.<p></p> Objective To examine the associations between body mass index (BMI) and waist-to-height ratio (WHtR) measured in childhood and adolescence and cardiometabolic risk factors in adolescence.<p></p> Methods Secondary data analysis of the Avon Longitudinal Study of Parents and Children, a population based cohort. Data from 2858 adolescents aged 15.5 (standard deviation 0.4) years and 2710 of these participants as children aged 7–9 years were used in this analysis. Outcome measures were cardiometabolic risk factors, including triglycerides, low density lipoprotein cholesterol, high density lipoprotein cholesterol, insulin, glucose and blood pressure at 15 years of age.<p></p> Results Both BMI and WHtR measured at ages 7–9 years and at age 15 years were associated with cardiometabolic risk factors in adolescents. A WHtR ≥0.5 at 7–9 years increased the odds by 4.6 [95% confidence interval 2.6 to 8.1] for males and 1.6 [0.7 to 3.9] for females of having three or more cardiometabolic risk factors in adolescence. Cross-sectional analysis indicated that adolescents who had a WHtR ≥0.5, the odds ratio of having three or more cardiometabolic risk factors was 6.8 [4.4 to 10.6] for males and 3.8 [2.3 to 6.3] for females. The WHtR cut-point was highly specific in identifying cardiometabolic risk co-occurrence in male children and adolescents as well as female children (90 to 95%), but had poor sensitivity (17 to 53%). Similar associations were observed when BMI was used to define excess adiposity.<p></p> Conclusions WHtR is a simple alternative to age and sex adjusted BMI for assessing cardiometabolic risk in adolescents

HAEMATOLOGICAL PARAMETERS IN EXOTIC COWS DURING GESTATION AND LACTATION UNDER SUBTROPICAL CONDITIONS

Seventy Holstein-Friesian and Jersey cows of different ages kept at the Livestock Experiment Station, Bhunikey (Pattoki), district Kasur, Pakistan were used for this study. These cows were divided into seven groups having 10 animals in each group. Group numbers 1 to 7 were named as pregnant heifers, pregnant lactating cows, non-pregnant dry cows, non-pregnant heifers, parturient cows, pregnant dry cows and non-pregnant lactating cows, respectively. Blood samples from all the animals were collected and haematological values were recorded, using routine haematological procedures. The highest Hb concentration (11.32 ± 0.32 gm/dl) was recorded in group-4, while the lowest (9.24 ± 0.35 gm/dl) was observed in group-7. The highest RBCs count and PCV (6.18 ± 0.47 x 106/µl and 35.51 ± 1.51%) were recorded in group-4 and the lowest (4.55 ± 0.26 x 106/µl and 29.23 ± 1.09%) values were observed in group-6. The highest MCV, MCH and MCHC (65.26 ± 1.96 fl, 23.50 ± 1.31 pg and 35.75 ± 0.99 gm/dl) were noted in group-5 and the lowest (55.16 ± 1.72 fl, 16.77 ± 1.14 pg and 30.09 ± 1.15 gm/dl) were noted in group-2. The highest ESR (7.60 ± 1.15 mm/24 hours) was recorded in group-6 and the lowest (4.89 ± 0.40 mm/24 hours) values were observed in group-5. The highest WBCs count (9.43 ± 1.15 x 103/µl) was observed in group-1 and the lowest (6.35 ± 0.72 x 103/µl) was recorded in group-5. Amongst DLC, highest (P<0.05) lymphocyte count (69.10 ± 2.55%) was observed in group-4, while lowest count (56.70 ± 5.16%) was in group-5. The differences between monocyte, neutrophil, eosinophil and basophil counts in all the groups were statistically non-significant

Drop size in a liquid pulsed sieve-plate extraction column

Peer reviewedPublisher PD