Comparative performance evaluation of a diesel engine run on diesel and biodiesel produced from coconut oil

Using renewable alternative fuel such as biodiesel in the diesel engines has long been advocated for. The aim of the study was to experimentally investigate and compare the performance in terms of fuel consumption rate, brake power, mechanical efficiency of a diesel engine individually fuelled by sole coconut oil biodiesel and diesel. All the tests were conducted using a test rig at different engine loads of 0, 25, 50, 75 and 100%. Results of the test revealed that fuel consumption rate of the engine when it was fuelled by coconut oil biodiesel were 3.651, 4.058, 4.465, 3.113 and 1.76litres/h and were 2, 1.55, 1.10, 1.06 and 1.02litres/h when the engine was fuelled by sole diesel at the respective aforementioned engine loads. The brake powers of the engine when biodiesel was used were found to be lower than when diesel was used at each load The mechanical efficiencies of the engine when biodiesel was used were found to be slightly lower at each load than when diesel was used. The fuel consumption rates of the diesel engine when fuelled individually with sole biodiesel and sole diesel were found to vary with load, brake power and mechanical efficiency of the engine. Brake power was also found to vary with load when the engine was fuelled individually with sole biodiesel and sole diesel.Keywords: Diesel engine, diesel, biodiesel, fuel consumption, performanc

Hierarchical multimodal hub location problem with time-definite deliveries

Hierarchical multimodal hub location problem is a cost-minimizing hub covering problem where two types of hubs and hub links, accounting for ground and air transportation, are to be established, while ensuring time-definite deliveries. We propose a mixed-integer programming formulation and perform a comprehensive sensitivity analysis on the Turkish network. We show that the locations of airport hubs are less sensitive to the cost parameters compared to the locations of ground hubs and it is possible to improve the service quality at not much additional cost in the resulting multimodal networks. Our methodology provides the means for a detailed trade-off analysis. © 2012 Elsevier Ltd

The single-allocation hierarchical hub-median problem with fuzzy flows

This paper addresses the problem of designing a hierarchical single-allocation hub-median (SA-H-HM) network considering fuzzy flows between nodes. The problem is modeled as a fuzzy mathematical programming model and a hybrid algorithm of population-based iterated local search (PILS) and fuzzy simulation is employed. Results clearly show that PILS is efficient in reaching solutions with virtually all the errors less than one percent to the optimal solutions. Moreover, the proposed PILS is capable to escape local optima. Finally, the results of the hybrid algorithm give insights about the problem under uncertainty

Body mass index and complications following major gastrointestinal surgery: A prospective, international cohort study and meta-analysis

Aim Previous studies reported conflicting evidence on the effects of obesity on outcomes after gastrointestinal surgery. The aims of this study were to explore the relationship of obesity with major postoperative complications in an international cohort and to present a metaanalysis of all available prospective data. Methods This prospective, multicentre study included adults undergoing both elective and emergency gastrointestinal resection, reversal of stoma or formation of stoma. The primary end-point was 30-day major complications (Clavien–Dindo Grades III–V). A systematic search was undertaken for studies assessing the relationship between obesity and major complications after gastrointestinal surgery. Individual patient meta-analysis was used to analyse pooled results. Results This study included 2519 patients across 127 centres, of whom 560 (22.2%) were obese. Unadjusted major complication rates were lower in obese vs normal weight patients (13.0% vs 16.2%, respectively), but this did not reach statistical significance (P = 0.863) on multivariate analysis for patients having surgery for either malignant or benign conditions. Individual patient meta-analysis demonstrated that obese patients undergoing surgery formalignancy were at increased risk of major complications (OR 2.10, 95% CI 1.49–2.96, P < 0.001), whereas obese patients undergoing surgery for benign indications were at decreased risk (OR 0.59, 95% CI 0.46–0.75, P < 0.001) compared to normal weight patients. Conclusions In our international data, obesity was not found to be associated with major complications following gastrointestinal surgery. Meta-analysis of available prospective data made a novel finding of obesity being associated with different outcomes depending on whether patients were undergoing surgery for benign or malignant disease