(The) study of ships' safety domain based on the Philippine navigators' risk perception index

Dimailig, Orlando S Mokpo National Maritime University 2018 국내박사

Abstract This paper conducted a study of the risk perception of the Philippine navigators while navigating the approaches to harbors, either maneuvering at inner harbor or outside harbor, but near coast. The aim is to construct an index on safety domain of the minimum safe distances relative to the ship’s four-cardinal sides when navigating within the proximity of hazards that may cause risk and danger to safe navigation. Being the major source of manpower in the maritime field and one of the sources of navigating officers, the paper chose the Philippine navigators as the subject of the study. The paper uses a descriptive research through questionnaire survey. It carried out the survey with the experienced navigators and collected 71 return responses wherein descriptive statistics, ANOVA and Cronbach’s Alpha, are used in testing the significance and content reliability. It also uses Pearson-Product Moment Correlation for comparing the variables, mostly the types of vessels, in relation with the adverse effects of restricted visibility, strong winds and currents in navigation. The statistical analysis is contained in Chapter 4. Chapter 2 presented the various related maritime traffic risk assessment and evaluation models presently in use or studied. It presents the transportation phenomena, difficulty in maneuverability caused by land and environmental stresses (ES), traffic phenomena, FSA, MARA, PMSC, US evaluation models. It also extensively demonstrates the IALA risk management tools, PAWSA and IWRAP. Chapter 3 lays out the data collected from the survey and presents them in graphical and tabulated forms. It, then, concludes with the outcome and recommends a continuum of this study to make full use of its findings. Among the outcomes of the study, the minimum safe distance was found to be strongly significant and there is reliable association with the variables. The perception of fear when measured from the different encountering scenarios and condition are almost constant in the four-cardinal sides of the ships. At inner harbor: ahead 7.0 LOA, stb’d 5.4 LOA, port 5.5 LOA and astern 5.9 LOA. When navigating at outer harbor, the results are: 7.7 LOA, 6.5 LOA, 6.4 LOA and 6.5 LOA, respectively. In the perceived level of fear, the dominant levels are ‘minimal’ at –1, and ‘considerable’, -2 which means that the navigators did not show undue fear perception when meeting vessels at inner harbor and in the periphery of port approaches. Key words : Ship’s domain, Minimum safe distances, Philippine navigators, Risk management, Risk perception index, ES model, Marine traffic

(A) study on torsional vibration characteristics of a direct coupled shaft generating system on low-speed two stroke diesel engine

Hoang, Nam Truong Mokpo National Maritime University 2017 국내석사

Abstract Nowadays, developments in world economy have led to drastic changes in strategy operation of the shipping and shipbuilding industries. Because of the great economic benefits, fuel oil saving has been one of the most important goals being pursued. The application of power take-off configurations are seen to increase fuel economy and are suitable for power generation. In this thesis, the dynamic properties of a shaft generator coupled on a low-speed two stroke diesel engine of an 18,600TEU container vessel is presented. The torsional measurement was performed during official sea trial of the vessel in Mokpo by using modern equipment and EVAMOS program developed by Dynamics Laboratory of Mokpo National Maritime University (MMU) to examine torsional resonance on the propulsion shafting system. Despite of the advantages of increased maximum explosion pressure and mean effective pressure, the risk of several complicated vibration problems due to increased exciting torque and stresses must be concerned. Torsional vibration damper was attached at the free end of crankshaft to adjust natural frequency of the system and reduce torsional vibration as well as protect shafting system. The generator is placed on the intermediate shaft, where the vibration caused by explosion pressure is less than on the main engine. A strain gage was installed on the generator shaft, combine with telemetric system, which were used in order to determine the variation of the vibratory torque. Furthermore, gap sensor was installed on turning wheel to determine angular velocity fluctuation. All measured data was recorded and analyzed by EVAMOS program. Through actual measurement, calculated and measured results can be compared to ensure whether there is any danger or not for the propulsion shafting system when the engine work in both normal firing condition and misfiring condition. In addition, angular velocity fluctuation for each vibration order is proportional to voltage variation. At a certain engine speed, the angular velocity fluctuation of an order can be calculated and compared with the limit on Simons curve to evaluate the quality of electric power produced by the shaft generator and the possibility of connecting this power to the ship main electric network. The result of this study suggests a review on existing classification rules for generator design and the lowering of angular velocity variation limit.

(The) quadruped robot TITAN-VIII control by gesture and speech recognition

Nguyen, Van Tien Mokpo National Maritime University 2018 국내박사

Abstract Nowadays, robots are so important in many fields of our life such as military, industrial products counter, explore, sport, traffic monitoring. Most the designed and developed of robots are to work in extreme environments such as ocean bottom, space and hazard prevention. It is not easy for the people living there because of the high atmosphere, the low temperature and the high risks for the life of people. However, the robots are capability of replacing people to reduce the risks. The robots are also separated into two types of Wheeled-robot and Legged-robot that depends on the mobility of the robot that is a wheel or a crawler, respectively. Legged robots (or Walking robots) have a potential to pass over certain types of terrain in a more efficient and stable manner more than the others, using wheels or tracks. Other advantageous properties of walking robots are that they cause less damage to the terrain, and they are omnidirectional, which gives them an advantage in moving through cluttered and tight environments. Besides them, the great development of computer vision technique can be applied into robots. The computer vision includes methods for acquiring, processing, analyzing, understanding the digital image and extracting information from images to control a real system of user. In the automation system, the image information can be used as sensor data to detect parameters of target image and control object tracking, following system. The combination between robot and computer vision technique is a today’s trend to make a smart system. A description of the implementation and experimental results are provided using the quadruped robot TITAN-VIII. The main contribution of the dissertation is in the analysis of the stability of balanced quadrupedal gaits statically and how statically balanced walking and the various posture of the robot is discussed to keep the robot always in the statically stable without mathematical model. Because of without a complex mathematical model of TITAN-VIII, a controller is added into system to help the robot moves to target smoothly and exactly. Based on above works, the math formulas are presented to determine the joint angles of the robot and simulate on Matlab & Simulink software. After that a program is created to recognize human gesture and speech. TITAN-VIII is equipped with one Microsoft's Kinect sensor which includes 3D scanner, color camera and depth sensor. TITAN-VIII is tested in real environment with normal light condition. Results of this dissertation are extremely impressive when TITAN-VIII can automatically and quickly avoid obstacles. From the success of experimental results, this control method can be applied into other similar smart robot easily and widely to develop new useful systems.

(A) study on water wheel type turbine for tidal energy extraction using numerical and experimental methods

Nguyen, Manh Hung Mokpo National Maritime University 2018 국내박사

Abstract Currently, there is no efficient and economical energy converter for the kinetic energy of shallow free surface flows available so far. Stream wheels or impulse type water wheels were employed in this role until the middle of the last century, and this type of water wheel could again be of interest today. However, there was still little information or knowledge of engineering and performance available for standardization of stream water wheel designs and manufactures. For this reason, engineers and researchers are now paying a lot of attention to stream water wheels once again to further their development. In this paper, an analysis of the performance and flow fields of stream water wheel turbines for tidal energy extraction is carried out using experimental and numerical methods. The purpose of which is to develop a water turbine suitable for sites, where fast and shallow surface flows are available, such as rivers or tidal currents. For both methods, the water wheel turbine is tested over a range of tip speed ratios with a differing number of rotor blades, ranging between three and twelve. Furthermore, the turbine’s performance is also evaluated by taking into account the effects of the blade working angles, submerged depths of the wheel in water (or bottom clearance), and blade shapes. Relying on that, the best turbine design is identified with the optimal number of blades, the most effective blade shape, blade’s working angle and bottom clearance of the wheel for tidal energy applications. These results are expected to contribute to the current knowledge on stream water wheels. The results indicate that the numerical simulation shows agreement with the experiment in most cases. Also, the water wheel turbine operates effectively at a range of small tip speed ratios, where the highest turbine efficiency is produced. With the same working conditions, the turbines using between six and nine blades generate a greater efficiency and cause lesser reverse flows than other turbines when submerged in water. In contrast, the 3-bladed turbine is the least efficient design as it produces the lowest amount of energy and causes intense vibrations and noises. These noises are a result of a collision between the incoming flow of the channel and the wheel blades during the experimentation, especially at high load conditions. By adding more blades, the torque generated is improved considerably; however, the upstream and downstream depths of the turbine, in this case, are also elevated significantly. Furthermore, in the inlet region, the 3-bladed and 6-bladed turbines have a smaller shock loss and a lower resistance to the main flow from the inlet than the others do. Meanwhile, it is found that the flow in the outlet region on the turbines with between nine and twelve blades is in the opposite direction to the wheel’s rotation, significantly obstructing the main flow from the inlet. Regarding the effect of bottom clearance (ε) of the blades on the device performance, it is found that the turbine considered generated the highest efficiency due to a blockage effect at a bottom clearance of 0.15 m. In contrast, at a bottom clearance of 0.55 m, the turbine performance reduced dramatically due to the water impulse area being lower than torque load. When lowering the wheel for working with water flows as well as minimizing the bottom clearance of the blade tip and test bed, the turbine could achieve the highest performance at a specific bottom clearance (ε = 0.15 m). However, when still reducing the bottom clearance, especially at ε ≤ 0.05 m, the wheel would have a drop in its performance due to an increase of secondary flows that hinder the reversal flow and leakage flow at the bottom and turn sharply to be against the main flow. Consequently, this phenomenon would affect harmfully to the wheel performance. Moreover, in the case study on the effect of the blade working angles, the wheel with blades inclined at an angle of 0 degrees was most efficient. The results also reveal that the turbine with α = -200 has air intruding at the inlet stage near the blade submerged in the water. Similar to the flow field analysis of the 3-bladed turbine in the study on the effect of turbine blade number on the performance, the presence of air in water may increase the complexity of the flow and may reduce the performance of this turbine. This phenomenon does not occur in the case of the blade with α = 00. The turbine with α = 200 also has a drop in the value of water volume fraction, but smaller at the inlet region than the wheel inclined at α = -200. For testing the effect of blade shape on the turbine performance, it is inferred that the straight blade showed the most noteworthy performance in comparison with other shapes. On the contrary, the curved blade produces the lowest efficiency in computation and experiment. Moreover, with the curved and Zuppinger shapes, the water impulse ability is small at the downstream depth of the turbine. In other words, this phenomenon would affect the turbine performance in an unfavorable tendency.

(A) study on the construction of new ship domain and consecutive waypoints generation method for automatic collision avoidance system of ship

Dinh, Gia Huy Mokpo National Maritime University 2017 국내박사

Abstract Automatic collision avoidance (ACA) system is an intensive discussion issue in the field of navigation. In the recent decade, maritime industry has been witnessed an unprecedented development. Giant ships are gradually mastering the sea. When traditional methods of transportation are no longer truly effective in the competition, new ones should be figured out. In order to meet this requirement, researchers have been thinking of upgrading automation system at shore or board which can facilitate mariners in the optimal maneuver. The topic of “automatic collision avoidance system”, therefore, becomes the most challenged to scholars over the world. This thesis introduces an automatic collision avoidance system integrated by three parts: watch keeping module which operates collection information of target ship (TS), a module to determine feasible collision avoidance action according to COLREG and a tracking module for keeping the own ship on the desired route. The evolution of proposed system is a cooperation between a new model of ship domain and a new ACA algorithm integrated into the second module for generating proper avoiding action. The effectiveness of the novel suggestion system is also evaluated in this research alongside the effective combination mentioned above in making avoidance action. The new ship domain model defining the most dangerous area around TS is shaped based on ship maneuverability information and good seamanship, within which statistical method is performed. 100 commercial vessels and 60 experienced officers are surveyed in order to determine parameters employed for ship domain construction. The new concept of automatic collision avoidance is adopted by mutually flexible application between PID controller and complexity rules of algorithm named Consecutive waypoint generation (CWPG) algorithm. Many simulation scenarios are then, utilized to validate the effectiveness and feasibility of the suggested system accompanying with the evaluation on saving energy and smoothness of the performance. A novel ACA system is presented in this thesis the effectiveness of which is convincing. The new ship domain model can be widely applied in general cases instead of certain restriction areas implementing surveys in previous studies. Its advantages are further demonstrated in the association with ACA algorithm for making collision avoidance route. Simulation scenarios are processed and approved to be effective in comparison with the simulated results of CWPG algorithm by a representative algorithm of previous studies. There is no fulfilled acceptance solution to the major until now, however, new approaching development of this research will promise a positive result for an application of ACA system in deploy in the future.

(A) study on real-time collision assessment zone based on potential risk ship domain

Luong, Tu Nam Mokpo National Maritime University 2020 국내박사

(The) application of image acquisition and processing using LabVIEW-based FPGA implementation to wheeled mobile robots

Vuong, Duc-Phuc Mokpo National Maritime University 2014 국내석사

(The) transient torsional vibration and fatigue strength of 2-stroke low speed diesel engine propulsion shafting system during barred speed range passage

Vuong, Quang Dao Mokpo National Maritime University 2019 국내박사

Design and computational analysis of counter-rotating tidal current turbine

Hoang, Anh Dung Mokpo National Maritime University 2015 국내박사

(A) study on application of metamaterials to control seismic and tsunami waves

Pham, Van Sy Mokpo National Maritime University 2016 국내박사

Earthquakes are a natural phenomenon, it is formed by the slide, breaking the surface and inside Earth. According to the The United States Geological Survey, there are about 1,000,000 earthquakes occurring around the world in a year. Earthquakes occur frequently unleash a huge energy and creates seismic waves. This wave creates damage to buildings and infrastructure as they move through. Not only that, the earthquake was one of the main reasons to form offshore tsunami. Earthquake and tsunami disaster that two people often face. It caused enormous losses of human lives and property. December 2004, magnitude earthquake occurred about 9.3 Ritcher, Indian Ocean, it has created a tsunami with wave heights of about 20 meters when approach a shore. According to estimates more than 200,000 people died and lost hundreds of millions of people affected as homeless ... In 2011, off the coast of Japan and an earthquake occurred with magnitude of about 9.0 Ritcher, then a tsunami wave was formed. According to estimates of organized Japan, approximately 15,000 people died in the tsunami, more than 300 bridges broken and so much other infrastructure ruined. This is also the earthquake, tsunami caused nuclear leakage. There are many buildings damaged by the displacement and relocation of the building which is caused by the displacement of the ground. The solution reduces the movement of building, displacements of structures during ground movement is one of the current methods are engineers build is capacitance. In addition to the damage being caused by the motion, other works damaged by the energy of the earth when the quake occurred on the building, to minimize the damage caused by this, engineers commonly used methods of energy absorption when designing structures So far, engineer’s coastal protection has many methods to prevent and mitigate the impact of the waves, but the methods to prevent the impact of the tsunami is still used seawall. In terms of structure, the barrier wall tsunami waves just another wall, but the height of the tsunami as it approached the coast is huge so a height tsunami wall is also huge. A new form seawall has a height change on the water level to be studied by a team of Japanese researchers. In 1968, Russian scientist published his study, he pointed out that it is possible to create materials with a negative refractive index. He laid the foundation for the development of metamaterials today. In recent decades, scientists have a lot of research on metamaterials and it also has a lot of achievements. A material that can adjust the path of the waves. But most of the studies are applied to electromagnetic waves, there are few studies on the acoustic wave and not have to publish applications in the construction field. In this study, two lenses with interesting properties, the lens has the ability to converge the rays at a point on the edge of the lens, often called lens Luneburg. Other lens capable of bending wave beam enters in the lens and turn back the broadcast source commonly known as Eaton lens 180, will be introduced and applied. The two lenses are research and development for electro-magnetic waves and it is made from homogeneous material are modified to obtain near refractive index as desired. Two lenses will be redesigned to be able to deploy the practical easier. The structure of the two lenses are constructed from steel bars with circular cross-sections for the two-dimensional lens and spherical for 3D. In the two-dimensional space of the different positions of the crystal size circular cross section will have different radii. Similarly, to the three-dimensional space, the different positions, the radius of the sphere will be different. For convergence Luneburg lens in two-dimensional space is built by the steel bars with circular cross-sections will be tested at some position to confirm the results of design and simulation.