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

Solving Travelling Thief Problems using Coordination Based Methods

A travelling thief problem (TTP) is a proxy to real-life problems such as postal collection. TTP comprises an entanglement of a travelling salesman problem (TSP) and a knapsack problem (KP) since items of KP are scattered over cities of TSP, and a thief has to visit cities to collect items. In TTP, city selection and item selection decisions need close coordination since the thief's travelling speed depends on the knapsack's weight and the order of visiting cities affects the order of item collection. Existing TTP solvers deal with city selection and item selection separately, keeping decisions for one type unchanged while dealing with the other type. This separation essentially means very poor coordination between two types of decision. In this paper, we first show that a simple local search based coordination approach does not work in TTP. Then, to address the aforementioned problems, we propose a human designed coordination heuristic that makes changes to collection plans during exploration of cyclic tours. We further propose another human designed coordination heuristic that explicitly exploits the cyclic tours in item selections during collection plan exploration. Lastly, we propose a machine learning based coordination heuristic that captures characteristics of the two human designed coordination heuristics. Our proposed coordination based approaches help our TTP solver significantly outperform existing state-of-the-art TTP solvers on a set of benchmark problems. Our solver is named Cooperation Coordination (CoCo) and its source code is available from https://github.com/majid75/CoCoComment: expanded and revised version of arXiv:1911.0312

Advanced control algorithm for FADEC systems in the next generation of turbofan engines to minimize emission levels

New propulsion systems in aircrafts must meet strict regulations and emission limitations. The Flightpath 2050 goals set by the Advisory Council for Aviation Research and Innovation in Europe (ACARE) include reductions of 75%, 90%, and 65% in CO2, NOx, and noise, respectively. These goals are not fully satisfied by marginal improvements in gas turbine technology or aircraft design. A novel control design procedure for the next generation of turbofan engines is proposed in this paper to improve Full Authority Digital Engine Control (FADEC) systems and reduce the emission levels to meet the Flightpath 2050 regulations. Hence, an Adaptive Network–based Fuzzy Inference System (ANFIS), nonlinear autoregressive network with exogenous inputs (NARX) techniques, and the block-structure Hammerstein–Wiener approach are used to develop a model for a turbofan engine. The Min–Max control structure is chosen as the most widely used practical control algorithm for gas turbine aero engines. The objective function is considered to minimize the emission level for the engine in a pre-defined maneuver while keeping the engine performance in different aspects. The Genetic Algorithm (GA) is applied to find the optimized control structure. The results confirm the effectiveness of the proposed approach in emission reduction for the next generation of turbofan engines

A Profit Guided Coordination Heuristic for Travelling Thief Problems

The travelling thief problem (TTP) is a combination of two interdependent NP-hard components: travelling salesman problem (TSP) and knapsack problem (KP). Existing approaches for TTP typically solve the TSP and KP components in an interleaved fashion, where the solution to one component is held fixed while the other component is changed. This indicates poor coordination between solving the two components and may lead to poor quality TTP solutions. For solving the TSP component, the 2-OPT segment reversing heuristic is often used for modifying the tour. We propose an extended and modified form of the reversing heuristic in order to concurrently consider both the TSP and KP components. Items deemed as less profitable and picked in cities earlier in the reversed segment are replaced by items that tend to be equally or more profitable and not picked in the later cities. Comparative evaluations on a broad range of benchmark TTP instances indicate that the proposed approach outperforms existing state-of-the-art TTP solvers

A profit guided coordination heuristic for travelling thief problems

The travelling thief problem (TTP) is a combination of two interdependent NP-hard components: travelling salesman problem (TSP) and knapsack problem (KP). Existing approaches for TTP typically solve the TSP and KP components in an interleaved fashion, where the solution to one component is held fixed while the other component is changed. This indicates poor coordination between solving the two components and may lead to poor quality TTP solutions. For solving the TSP component, the 2-OPT segment reversing heuristic is often used for modifying the tour. We propose an extended and modified form of the reversing heuristic in order to concurrently consider both the TSP and KP components. Items deemed as less profitable and picked in cities earlier in the reversed segment are replaced by items that tend to be equally or more profitable and not picked in the later cities. Comparative evaluations on a broad range of benchmark TTP instances indicate that the proposed approach outperforms existing state-of-the-art TTP solvers

Transition Constraints for Parallel Planning

We present a planner named Transition Constraints for Parallel Planning (TCPP). TCPP constructs a new constraint model from domain transition graphs (DTG) of a given planning problem. TCPP encodes the constraint model by using table constraints that allow don't cares or wild cards as cell values. TCPP uses Minion the constraint solver to solve the constraint model and returns the parallel plan. Empirical results exhibit the efficiency of our planning system over state-of-the-art constraint-based planners

Preventive Effects of Pre- and Intra-operative Marcaine, Lidocaine, and Marcaine Plus Lidocaine on Pain Relief in Lumbar Disc Herination Open Surgery

Background: As marcaine is administered to a great extent due to minor complications and reasonable expenses and as discectomy is prevalently used in Iran, this study makes a comparison between effect of marcaine alone, lidocaine alone, and marcaine plus lidocaine on pain relief of patients undergoing lumbar disc open surgery. Materials and Methods: In a clinical trial study, 192 patients were selected and randomly divided into four groups. Patients in Groups 1–4 received 0.5 ml marcaine during surgery, 5 ml lidocaine 2% before incision, 5 ml lidocaine 2% before incision plus 5 ml marcaine during surgey and normal saline, respectively. After patients gained knowledge of visual analog scale (VAS) criteria, their severity of pain was measured and was recorded in their profiles, along with demographic details and history of diseases. After surgery and their transfer to their rooms, their severity of pain was measured and recorded again by using VAS criteria. Finally, difference between the four groups was compared by SPSS software. Results: The mean (±standard deviation) of postoperative pain in marcaine + lidocaine, marcaine, lidocaine, and normal saline was 3.5 ± 1.3, 3.5 ± 1.6, 36.1.9, and 4.2 ± 1.8, respectively, and we did not observe any significant difference in severity of pain after surgery in these groups (P = 0.15). The highest and lowest degree of satisfaction occurred in marcaine-lidocaine group and control group, respectively, (40 patients [83.3%] vs. 25 patients [52.1%]). Conclusion: Lidocaine-marcaine treatment reduces the need to opiates in cases of postoperative pain relief of discectomy and provides patients with great satisfaction

Hepatitis B Virus Surface Antigen Variants Clustered Within Immune Epitopes in Chronic Hepatitis B Carriers from Hormozgan Province, South of Iran

Objective(s)The aim of this study was to characterize the hepatitis B virus surface protein genotypes and sequence variations among hepatitis B virus surface antigen (HBsAg) positive chronic patients in Hormozgan province, south of Iran.Materials and MethodsA total of 8 patients enrolled in this study. The surface gene was amplified and directly sequenced. Genotypes and nucleotide/amino acid substitutions were identified compared to the sequences obtained from the database.ResultsAll strains belonged to genotype D. Overall 77 “muta¬tions” occurred at 45 nucleotide positions, of them, 44 (57.14%) were silent (no amino acid altering) and 33 (42.86%) were missense (amino acid changing). A number of 24 (80%) out of 30 amino acid changes occurred in different immune epitopes within surface protein, of which, 9 (30%) in B cell epitopes in 7 residues (2 occurred in “a” determinant region); 8 (42.1%) in T helper epitopes in 7 residues and 7 (10%) in 4 residues inside CTL epitopes.ConclusionHepatitis B virus genome containing mutated immune epitopes no longer could be recognized by specific T-cells of the host immune surveillance and did not enhance anti-HBs production. This could led to the progression of chronicity of hepatitis B virus infection