1,254 research outputs found
Toward monitoring and estimating the size of the HFO-contaminated seabed around a shipwreck using MBES backscatter data
No full textFunding Information: The authors are grateful to three anonymous reviewers for their constructive criticism and valuable comments. The authors express their gratitude to the Maritime Institute in Gdansk for making the final version of the report (Maritime Institute in Gdansk, 2016) available. The second author appreciates the support of the Gdynia Maritime University in funding this research through internal grant WN/PZ/2021/02. Funding Information: The second author appreciates the support of the Gdynia Maritime University in funding this research through internal grant WN/PZ/2021/02 . Publisher Copyright: © 2021Despite a progressive reduction of oil spills caused by the activity of maritime transportation, the latent sources of pollution still exist. Although the harmful impact of heavy fuel oil (HFO) on the marine environment is widely known, many shipwrecks cause contamination of the surrounding areas. In this paper, an approach to monitor the area of the HFO spill around a shipwreck is made using a bottom backscattering strength (BBS) obtained by a multibeam echosounder (MBES). As a case study, the s/s Stuttgart wreck located in the Gulf of Gdansk (Poland) is verified. Two different measurement campaigns have been carried out in shallow waters using low (190 kHz) and high (420 kHz) MBES frequency. The results indicate that the polluted area around s/s Stuttgart was estimated at 49.1 ha, which is around 18.3% more in comparison to the geological surveys made four years earlier.Peer reviewe
The Weight and Hopcount of the Shortest Path in the Complete Graph with Exponential Weights
No full textBoth the hopcount HN (the number of links) and the weight WN (the sum of the weights on links) of the shortest path between two arbitrary nodes in the complete graph KN with i.i.d. exponential link weights is computed. We consider the joint distribution of the pair (HN,WN) and derive, after proper scaling, the joint limiting distribution. One of the results is that HN and WN, properly scaled, are asymptotically independent.Delft Institute of Applied MathematicsElectrical Engineering, Mathematics and Computer Scienc
Feasibility of abdominoplasty with Cesarean section [Retraction]
No full textThe Editor-in-Chief and Publisher of the International Journal of Women’s Health have been alerted by Dr Nadine Sherif, the corresponding author, to unacceptable levels of duplication with a previously published paper: Ali A, Essam A. Abdominoplasty Combined with Cesarean Delivery: Evaluation of the Practice. Aesthetic Plastic Surgery. 2011;35(1):80–86.It is worth noting that this paper was peer-reviewed by two peer-reviewers and the Editor-in-Chief of the International Journal of Women’s Health before publication. The paper concerned is: Thabet WN, Hossny AS, Sherif NA. Feasibility of abdominoplasty with Cesarean section. International Journal of Women’s Health. 2012;4:115–121
A concept of critical safety area applicable for an obstacle-avoidance process for manned and autonomous ships
No full textFunding Information: This research work was supported by the Gdynia Maritime University internal grant WN/PZ/2021/02. Funding Information: The author is grateful to three anonymous reviewers for their constructive criticism and valuable comments. The author expresses his gratitude to Prof. Jerzy Matusiak of Aalto University for making the LaiDyn code available, as well as to Dr. Tomasz Hinz of Waterborne Transport Innovation Foundation for preparing LaiDyn output files containing ship trajectories. This research work was supported by the Gdynia Maritime University internal grant WN/PZ/2021/02. Publisher Copyright: © 2021 The Author(s)In times of increased automation of maritime transportation, ship collision with a stationary obstacle (allision) remains a significant problem. There are many existing solutions rooted primarily in the concept of ship domain and path-planning algorithms. However, among these, a geometrical approach to the determination of a required maneuvering area considering the dynamic nature of ship operations in close-quarters situations is still missing. Therefore, an improved concept of the CADCA (Collision Avoidance Dynamic Critical Area) is introduced for the case of ship allision. The CADCA is a deterministic zone that geometrically delimits required maneuvering space of a vessel. Its shape changes depending on the operational parameters of a ship, such as the magnitude of rudder angle, initial forward speed, or planned alteration of the course. In contrast to ship domain, the CADCA is determined using the critical distance between two objects called MDTC (Minimum Distance to Collision). Therefore, the CADCA concept can be used to appoint a position of no-return in a close-quarters situation, so as to determine the time and distance of the last-minute maneuver. An improved method of CADCA determination is introduced, along with an investigation of operational factors influencing the ship's critical area in allision scenarios. The simulations have been conducted for large passenger and container ship in encounters with various stationary obstacles differing in size and shape. The results indicate that from the operational point of view, a deflection of the rudder is the most influencing factor on the size of the CADCA, while the impact of ship speed is negligible for the investigated vessels. Besides, various applications of the CADCA are proposed and discussed for both manned and prospective autonomous vessels.Peer reviewe
Gait characteristics of subjects with chronic fatigue syndrome and controls at self-selected and matched velocities
No full textBackground:
Gait abnormalities have been reported in individuals with Chronic Fatigue Syndrome (CFS) however no studies exist to date investigating the kinematics of individuals with CFS in over-ground gait. The aim of this study was to compare the over-ground gait pattern (sagittal kinematics and temporal and spatial) of individuals with CFS and control subjects at their self-selected and at matched velocities.
Methods:
Twelve individuals with CFS and 12 matched controls participated in the study. Each subject walked along a 7.2 m walkway three times at each of three velocities: self-selected, relatively slow (0.45 ms-1) and a relatively fast (1.34 ms-1). A motion analysis system was used to investigate the sagittal plane joint kinematics and temporal spatial parameters of gait.
Results:
At self-selected velocity there were significant differences between the two groups for all the temporal and spatial parameters measured, including gait velocity (P = 0.002). For the kinematic variables the significant differences were related to both ankles during swing and the right ankle during stance. At the relatively slower velocity the kinematic differences were replicated. However, the step distances decreased in the CFS population for the temporal and spatial parameters. When the gait pattern of the individuals with CFS at the relatively fast walking velocity (1.30 ± 0.24 ms-1) was compared to the control subjects at their self-selected velocity (1.32 ± 0.15 ms-1) the gait pattern of the two groups was very similar, with the exception of both ankles during swing.
Conclusion:
The self-selected gait velocity and/or pattern of individuals with CFS may be used to monitor the disease process or evaluate therapeutic intervention. These differences may be a reflection of the relatively low self-selected gait velocity of individuals with CFS rather than a manifestation of the condition itself
Retrospective review of the drop in observer detection performance over time in lesion-enriched experimental studies.
No full textThe vigilance decrement describes a decrease in sensitivity or increase in specificity with time on task. It has been observed in a variety of repetitive visual tasks, but little is known about these patterns in radiologists. We investigated whether there is systematic variation in performance over the course of a radiology reading session. We re-analyzed data from six previous lesion-enriched radiology studies. Studies featured 8-22 participants assessing 27-100 cases (including mammograms, chest CT, chest x-ray, and bone x-ray) in a reading session. Changes in performance and speed as the reading session progressed were analyzed using mixed effects models. Time taken per case decreased 9-23% as the reading session progressed (p < 0.005 for every study). There was a sensitivity decrease or specificity increase over the course of reading 100 chest x-rays (p = 0.005), 60 bone fracture x-rays (p = 0.03), and 100 chest CT scans (p < 0.0001). This effect was not found in the shorter mammography sessions with 27 or 50 cases. We found evidence supporting the hypothesis that behavior and performance may change over the course of reading an enriched test set. Further research is required to ascertain whether this effect is present in radiological practice
Sex Differences in the Discriminative Stimulus Characteristics and Conditioned Enhancing Effects of a Morphine Occasion Setter in Rats
No full textThe current study explored the capacity for an interoceptive morphine stimulus to acquire enhanced appetitive properties via associative mechanisms from a perspective of sex-differences. Male and female Sprague-Dawley rats were assigned to a feature positive (FP) or feature negative (FN) group and all received daily intermixed morphine (3.2mg/kg, IP) or saline sessions. For FP rats, on morphine sessions, each of eight 15-sec white noise (WN) presentations was followed by access to sucrose; on saline sessions, WN was still presented, but sucrose was withheld. FN rats were trained on the reverse contingency. FP discrimination was acquired faster than FN discrimination, and females became sensitized to the locomotor effects of morphine, which did not influence conditioned responding when compared to males. Drug dose generalization testing with a series of morphine doses (0.0, 0.5, 1.0, 2.1, 3.2, 5.4, 6.5, 7.5 mg/kg) determined there were no sex differences in dose generalization for FN groups; for FP rats, the dose response curve for females was shifted to the right compared to that of males. FP females exhibited enhanced responding at a dose higher than that of their original training. In a separate cohort of male rats, morphine intravenous self-administration was assessed after learning the Pavlovian drug discrimination. An appetitive learning history with morphine resulted in greater morphine self-administration than a non-appetitive history. These results indicate that the discriminative stimulus characteristics of an interoceptive drug stimulus can be sex-dependent, and that learning history with a drug impacts the self-administration pattern with that drug
Total or Partial Knee Arthroplasty Trial - TOPKAT : study protocol for a randomised controlled trial
No full textPeer reviewe
Corrosion prevention of stell structures for Sri Lanka Author Premachandrasiri, W.N.
No full textSri Lanka has made a significant development in the design and construction sector during the last 10 years. The use of steel is one of the governing construction materials in the industries. One of the major concerns of existing steel structures is the durability. Corrosion and deterioration have become major challenges in the lifetime of the structure, as it is one of the major public focuses on the structures.
Standards are intended to assist engineers and corrosion experts in adopting best practice in corrosion protection of structural steel at new constructions with proper identification of an actual exposure. There are six environmental corrosivity categories according to BS ISO 12944 as C1, C2 C3, C4, C5 and C5 –M. Those are according to BS standard and they should be adapted for Sri Lanka. In this research environmental corrosivity category of SC1, SC2, SC3 and SC4 are classified for Sri Lanka considering corrosion affecting factors temperature, rainfall, coastal region and industrial zones. A field survey was carried out in different locations of the structure in the country to identify the pattern of corrosion according to variation of corrosion affecting factors.
Among the methods used to clean the surface of the steel before applying corrosion protection, sand blasting cleans best. However, it cannot be carried out in every location due to environmental issues and equipment required. Steel surface is difficult to clean using light tools because temporary stabilized corroded layer on the steel surface. If we change this surface (Convert surface grade A to Surface grade B), the light tools can be used for the surface preparation. Therefore a new method is proposed to change this surface grade. Firstly, sea water is sprayed on to the surface to increase the rate of corrosion and left for a day for rust to appear. Then it is cleaned by fresh water and surface salinity level should be checked using salinity meter. Then the surface can be prepared using “Cup-Brush application” method without using sand blasting. By this method well cleaned surface can be obtained and then the surface protection primer is applied on it immediately. This surface protection primer type and primer and paint thickness should be defined according to environmental corrosivity category
My Favorite Integer Sequences
No full textAbstract. This paper gives a brief description of the author's database of integer sequences, now over 35 years old, together with a selection of a few of the most interesting sequences in the table. Many unsolved problems are mentioned
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