Rendezvous Planning for Multiple Autonomous Underwater Vehicles using a Markov Decision Process

Multiple Autonomous Underwater Vehicles (AUVs) are a potential alternative to conventional large manned vessels for mine countermeasure (MCM) operations. Online mission planning for cooperative multi-AUV network often relies or predefined contingency on reactive methods and do not deliver an optimal end-goal performance. Markov Decision Process (MDP) is a decision-making framework that allows an optimal solution, taking into account future decision estimates, rather than having a myopic view. However, most real-world problems are too complex to be represented by this framework. We deal with the complexity problem by abstracting the MCM scenario with a reduced state and action space, yet retaining the information that defines the goal and constraints coming from the application. Another critical part of the model is the ability of the vehicles to communicate and enable a cooperative mission. We use the Rendezvous Point (RP) method. The RP schedules meeting points for the vehicles throughput the mission. Our model provides an optimal action selection solution for the multi-AUV MCM problem. The computation of the mission plan is performed in the order of minutes. This quick execution demonstrates the model is feasible for real-time applications

Analysis of fatigue behaviour of stainless steels under hydrogen influence

Three stainless steels – ASTM 304, 316 and 316L - used in hydrogen utilization equipment are under investigation at conditions of tension-compression, rotating-bending and fretting fatigue. Fatigue tests are carried out with hydrogen charged and uncharged specimens. Hydrogen charging includes cathodic type of charging and exposure to high pressure hydrogen gas. The experiments under rotating bending and tensioncompression fatigue are conducted under different frequencies in three different laboratories: at The University of Chemical Technology and Metallurgy, Sofia, Bulgaria; at Sandia National Laboratory, California and The University of Tufts, Medford, Massachusetts, USA; The HYDROGENIUS Institute at Kyushu University, Japan. The fretting fatigue tests are presented by The HYDROGENIUS Institute at Kyushu University, Japan. The obtained results are presented in Wöhler curves complemented by plots "Short fatigue crack length– Number of cycles" and “Tangential force coefficient–Stress amplitude”. The found fatigue characteristics are analyzed and compared at different loading conditions, showing the best performance of Steel 316L

Restaging role of 18F-FDG-PET/CT in a patient with a Malignant Peripheral Nerve Sheath Tumor (MPNST) caused by neurofibromatosis – case report

Malignant Peripheral Nerve Sheath Tumors (MPNST) are a malignant disease that originates in the cells that cover and protect the peripheral nerves. They are a rare disease, accounting for 6% of soft tissue sarcomas. We present a patient with a malignant peripheral nerve sheath tumor on the left brachium with neurofibromatosis. The patient underwent whole body PET/CT for restaging after total extirpation of a tumor formation originated from n. musculocutaneous in 09.2017, an excision of a recurrent tumor formation in the proximal half of the brachium invading into m. biceps brachii in 12.2017, a performed MRI in 02.2018 - with data for multiple MPSNT in the area between the two previous operations - and subsequent definitive radiotherapy (boost) in the area of the tumor formation and 6 cycles of chemotherapy with Epirubicin. After restaging PET/CT scan of the whole body was performed, progression of the disease was defined - increased in size and activity subpleural lesion in the lower lobe of the right lung

GC-MS analysis and antibacterial activity of some fractions from Lagochilus ilicifolius Bge. grown in Mongolia

3-methyl-1,2,3,4-tetrahydroquinoline (1), 4-hydroxyisoquinoline (2), 4-(1E)-hydroxy-1-prophenyl)-2-methoxyphenol (3), 4-acetoxycinnamic acid (4), Songoramine (5), and Songorine (6) have been determined by GC-MS analysis from the crude alkaloid mixtures (G1) obtained from the aerial parts of Lagochilus ilicifolius Bge. grown in Mongolia and comparison of the measured data with those from the literature. The compounds 1-6 are described for the first time from L.ilicifolius. From these 3-methyl-1,2,3,4-tetrahydroquinoline (1) was determined for the first time from natural plants.In addition, the antibacterial activity of fractions and total alkaloids were evaluated against Staphylococcus aurous, Bacillus subtilis, Bacillus cereus and Escherichia coli strains, respectively. The growth inhibition zones against gram-positive S.aureus, B.subtilis, B.cereus and gram negative E.coli, strains were observed. Positive results were achieved on 500 μg/disc concentration, but lower results or no active on 100 μg/disc concentration were for the plant extracts, fractions and total alkaloids.Mongolian Journal of Chemistry 16 (42), 2015, 39-4

Effect of treatment with enrofloxacin and Lactobacillus probiotics on ABCB1, ABCC2 and ABCG2 mRNA expression in poultry

Poultry feed is often supplemented by Lactobacillus probiotics which may alter drug bioavailability by affecting the expression of intestinal ATP-binding cassette (ABC) efflux transporters. Therefore the effect of probiotics, administered alone or in combination with enrofloxacin, on the expression of ABCB1, ABCC2 and ABCG2 mRNAs in chickens was evaluated. Day-old Ross chicks (n=24) were divided in four equal groups. Control group was not treated. The second group received feed with addition of probiotics Lactobacillus brevis, L. plantarum and L. bulgaricus 5 days after hatching, for 15 days. The third group received probiotics as described above and enrofloxacin at the age of 15 days (10 mg/kg, via drinking water for 5 days). The last group received enrofloxacin at age of 15 days (10 mg/kg, via drinking water for 5 days). Expression of ABC transporters in liver, duodenum and jejunum was determined by qRT-PCR. Down-regulation of ABCG2 mRNA in the liver (P<0.05), its up-regulation in the duodenum (P<0.05) and increased ABCB1 mRNA levels in the jejunum (P<0.05) can be attributed to enrofloxacin treatment. Decrease in ABCC2 mRNA expression in the duodenum can be associated with enrofloxacin administration. The observed changes were related to enrofloxacin administration and to lesser extent to Lactobacillus supplementation

On fatigue behaviour of two spring steels. Part II: Mathematical models

Symmetric fatigue in two spring steels is investigated in three groups of specimens. One of the groups (Steel EN10270-1SH/ DIN 17223C – C 0.82%, Mn 0.76%, Si 0.26%) has experienced rotating-bending fatigue in air, and the other two groups (Steel BS250A53/ DIN 55Si7 – C 0.56%, Mn 0.81%, Si 1.85%), torsion fatigue in-air and corrosion environment. All experiments include testing to fracture, applying acetate-foil replication technique, replica monitoring of short crack surface growth, length measuring of propagating cracks, a, at the corresponding number of fatigue cycles, N. Data obtained from replica monitoring are presented in plots “Crack lengths, a – Cycles, N”, and used for calculating fatigue crack growth rates, da/dN, and graphical presentations “Crack growth rates, da/dN – Crack lengths, a”. A mathematical description of da/dN – a is presented by introducing a parabolic-linear model in different versions for each of the steels. The model versions are verified through comparing the experimental fatigue lifetimes with those calculated by the proposed model version

On fatigue behavior of two spring steels. Part I: Wöhler curves and fractured surfaces

Symmetric fatigue in two spring steels is investigated in three groups of specimens. One of the groups (Steel EN10270-1SH/ DIN 17223C – C 0.82%, Mn 0.76%, Si 0.26%) has experienced rotating-bending fatigue in air, and the other two groups (Steel BS250A53/ DIN 55Si7 – C 0.56%, Mn 0.81%, Si 1.85%), torsion fatigue in-air and corrosion environment. Fatigue life-time data are obtained for both spring steels, and their corresponding Wöhler curves plotted and mathematically described. Surface short fatigue cracks are observed from origin to fracture by using acetate-foil replication technique, and their length, a, measured at the corresponding number of fatigue cycles, N. Those data are presented in plots “Crack lengths, a – Cycles, N” and a comparison made between both the steels. The fractured surfaces of all specimens have been studied and analyzed by the scanning-electron microscopy method