Research on Improving the Working Efficiency of Hydraulic Jet Submarine Cable Laying Machine

The anchoring and hooking of ships, bedrock friction and biological corrosion threaten the safety and stability of submarine cables. A hydraulic jet submarine cable laying machine manages to bury the submarine cables deep into the seabed, and effectively reduces the occurrence of external damage to the submarine cables. This machine uses a hydraulic jet system to realize trenching on the seabed. However, the hydraulic jet submarine cable laying machine has complicated operation and high power consumption with high requirements on the mother ship, and it is not yet the mainstream trenching method. In this paper, a mathematical model for the hydraulic jet nozzle of the submarine cable laying machine is established, and parameters that affect the trenching efficiency are studied. The effects of jet target distance, flow, angle and nozzle spacing on the working efficiency of the burying machine are analyzed by setting up a double-nozzle model. The results of the theory, numerical simulation and experiment show that the operational efficiency of the hydraulic jet submarine cable laying machine can be distinctly improved by setting proper jet conditions and parameters.

Towfish Attitude Control: A Consideration of Towing Point, Center of Gravity, and Towing Speed

This paper deals with the attitude control of a towfish (underwater towed vehicle) with two elevators and a single rudder to improve the image quality of an attached sound navigation ranging (sonar) system. Image distortion can occur if the towfish shakes excessively. Since a towfish is connected to the mother ship through a towing cable and the motion of the towfish is affected not only by the motion of the cable, but also by the position of the center of gravity, towing point, and towing speed, it is necessary to analyze how these factors affect the towfish to appropriately control its attitude. In this study, a method for obtaining a feasible region of the towing point in accordance with the variations in the center of gravity and towing speed is proposed, and the feasible region obtained can ensure that pitch control can be achieved using the installed elevators. In addition, the allowable range of disturbances for yaw control was also investigated. Simulations were conducted using the dynamic models of the towfish and cable to check the obtained feasible region/range, and it was confirmed that there is a region/range where the attitude control can be carried out with relative ease.

Operational Feasibility Study of High Altitude Balloon Platform based on the Wind Environment in South Korea

Naval helicopters flying at extremely low altitudes often face communication problems when the helicopter is located in the distance from the mother ship. Accordingly, new attention is being cast on the high altitude balloon (HAB) to solve this problem due to its cost-effectiveness and ability of rapid deployment to the battlefield. The balloon is one of a lighter-than-air vehicle that the blowing wind determines its speed, direction, and travel distance. Therefore, it is likely that seasonal changes in wind conditions will restrict the operation of the balloon. In this paper, the feasibility study of the balloon, which is regarded as a future communication relay platform, on the theater of operation of the Republic of Korea Navy the First Fleet was performed. The trends of the balloon trajectory for five years (2014 ~ 2018) with respect to seasonal wind variations were investigated employing the numerical trajectory prediction program. Simulated balloon trajectories of summer and winter showed considerable differences due to seasonal wind. Summer season was found that it has the most favorite flight environment for the balloon campaign. Upon reflecting on the simulation results, the HAB operating procedure, which capitalised on the Ulleungdo, was also suggested.

Systematic review of organizational models for intra-arterial treatment of acute ischemic stroke

Background Intra-arterial treatment of acute ischemic stroke requires changes to acute stroke services since most hospitals do not have on-site intra-arterial treatment facilities. Aim To identify models for delivery of intra-arterial treatment and to compare process performance and clinical and radiological outcomes of the different models. Methods We systematically searched the literature and contacted experts in the field. We performed a qualitative synthesis to identify models, and a quantitative review and meta-analysis of clinical and radiological outcomes under different organizational models. Summary of review The searches retrieved 148 publications, of which 27 were used for the identification and description of models, and 9 for the comparison of the different models. We identified four main models: the mother-ship, drip-and ship, mobile interventionist, and mobile stroke unit models. There were no randomized-controlled trials of the different models, but non-randomized comparisons were possible using data from 8 observational studies and 1 randomized-controlled trial of intra-arterial therapy, of a total of 4127 patients. Comparison between the mother-ship and drip-and-ship models showed no difference in survival (OR 0.81; 95% CI 0.63–1.03), favorable functional outcome (OR 0.96; 95% CI 0.73–1.25), or arterial patency (OR 0.89; 95% CI 0.73–1.08). Conclusions Different organizational models exist for intra-arterial treatment of acute ischemic stroke, but there is insufficient evidence to recommend a particular, universal model. Until one model can be shown to be superior, the choice of model should depend on local factors and patient characteristics.

Prise en charge des infarctus cérébraux

La prise en charge de l’infarctus cérébral aigu s’est considérablement améliorée ces dernières années grâce à de nouvelles techniques combinant imagerie et nouveaux traitements. La formalisation d’un parcours spécifique, multidisciplinaire (neurologues, radiologues, urgentistes et réanimateurs), a permis un véritable gain d’efficacité. Une course contre la montre s’enclenche dès les premiers signes cliniques évocateurs d’un accident vasculaire cérébral. L’approche thérapeutique actuelle, combinant thrombectomie et fibrinolyse dans les six premières heures après l’apparition des symptômes, a transformé le pronostic. Très récemment, des études rapportent un bénéfice de la thrombectomie jusqu’à 24 heures du début des symptômes chez des patients très sélectionnés. En outre, l’accès rapide à une unité neurovasculaire (UNV) est déterminant dans la réduction de la morbidité et du handicap, en dehors de tout traitement spécifique de recanalisation (effet stroke center). Ces nouvelles données impactent considérablement le schéma organisationnel des premières heures, définissant deux stratégies d’orientation du patient : transfert direct (mother ship) dans un centre associant UNVet centre de neuroradiologie interventionnelle (NRI) ou accueil dans une UNV et transfert secondaire dans un centre de NRI si nécessaire (drip and ship).