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Chen Y.-Y.,NSYSU | Chen Y.-Y.,International Wave Dynamics Research Center | Chen H.-S.,NSYSU
Ocean Engineering | Year: 2014

A three-dimensional (3D) Lagrangian solution up to the fifth-order is found for the Boundary Value Problem (BVP) of irrotational, progressive water waves propagating in the presence of uniform current in water of constant depth. The BVP is formulated in the Lagrangian framework which uses Lagrangian label (a,b,c) and time t as the independent variables. The (a,b,c) of a particle in wave motion are the coordinates of the particle position in the still water. In the solution, wave-current interaction is embedded in the Lagrangian velocity potential in such way that pressure is not affected by current in the wave-current field. In this study, we present motion properties of particles such as the particle motion period, drift velocity, the Lagrangian mean level, and the 3D particle trajectory and streakline, aspects that are hardly described by the Eulerian solution. It is found that the particle motion period is always larger than the progressive wave period. As the wave-current becomes steady motion, the stable wavy track of the particle motion may exist in the wave-current field. When currents vanish, the present solution deduces to the same solution of the progressive wave propagation by Chen et al. (2010). © 2014 Elsevier Ltd.

Applied Mechanics and Materials | Year: 2013

For an offshore platform applied to wave-energy conversion system, in order to catch the maximum waves to generate more powers, similar to wind-energy power generators, a range of angles for the devices normal to the propagating direction of incident waves is required, particularly when the power converting system has directional preference. A single mooring system would allow the offshore wave-energy conversion system to turn freely in accordance to the action of strong directions of propagating waves and in this way, most energy induced from the incident waves can be caught and converted into reusable powers. The aim of this study is to find the efficiency of single-moored platform applied to a wave power converting system through an experimental test in the water tank. © (2013) Trans Tech Publications, Switzerland.

Chen Y.-Y.,NSYSU | Chen H.-S.,NSYSU | Lin C.-Y.,NSYSU | Li M.-S.,NSYSU
Journal of Atmospheric and Oceanic Technology | Year: 2013

Experiments are conducted to measure the motion properties of water particle for the progressive water wave propagation in the presence of following and adverse uniform currents. The experimental data are used to validate the fifth-order Lagrangian solution from Chen and Chen. The experimental results show that the measured data of the particle motion properties such as the b line (denoted as the line connecting the positions of consecutive particles of the same b label), the particle velocity, the particle transport velocity (drift velocity), the particle trajectory, the particle motion period, and the Lagrangian mean level are in close agreement with those of the fifth-order Lagrangian solution. The study also shows that the particle label could adopt the position coordinates of the particle as if it were in still water. The motion of the b line oscillates like wave motion: its wavelength is equal to the progressive wavelength and its wave velocity obeys the Doppler effect so the sum of the velocities of the progressive wave and current, the particle motion period, the Lagrangian mean level, and the particle transport velocity less current velocity are the same as for the case of pure progressive waves.For following currents, the shape of particle trajectory depends on the horizontal particle velocity at the trajectory trough. For adverse currents, the shape of particle trajectory depends on the horizontal particle velocity at the trajectory crest.For a description of the flow motion, the Lagrangian solution could be more effective and precise than the Eulerian solution. © 2013 American Meteorological Society.

In this study, a protection-pipe system has been developed for the protection of undersea electricity cable layout along shoreline with medium deep water. The protection pipes are made of cast-iron alloys while the dimensions are designed corresponding to the balk diameter of electricity cables. The water depth of the area with cable layout is ranged from several meters to a hundred meters, where berthing anchoring from commercial ships and towing operation from fishing boats are constantly found. Therefore, to make sure that the protection pipe can work dependably against the loadings mainly from the operation as was mentioned, both analytical analysis and experimental tests were carried out. In the experimental studies, the full-scale model of several sets of protection-pipe system was tested for impact loadings. It was found from the results of both the analysis and experimental tests that the protection-pipes are able to meet the requirements of the local power company TPC set for the cable layout under seawater. © (2011) Trans Tech Publications.

Quadir B.,NSYSU | Chen N.-S.,NSYSU
Proceedings - 2013 IEEE 13th International Conference on Advanced Learning Technologies, ICALT 2013 | Year: 2013

The purpose of this study was to gain greater insights into the habit factors that contribute to one's learning effectiveness. Therefore, present study developed the 'Learner's Digest' blog (i.e., a learning blog) with relevant features including information retrieval, user friendly context and learner-learner interaction. It was designed to provide interesting blog posts to facilitate meaningful learning. In 'Learner's Digest' blog learners were participated as blog readers. This paper investigated how one's reading habit contributes to his/her learning effectiveness participating towards Learner's Digest blog. A survey was conducted for understanding the relationship between individual's reading habit, in terms of the reading attitude / behavioral pattern, and the learning effectiveness of participation towards a learning blog, in terms of learning performance and satisfaction. A total of 73 blog readers from 'Learner's Digest' participated in the study. Hypotheses were tested and data was analyzed using simple linear regression and logistic regression analysis. The result revealed that reading habit is a significant predictor of learning effectiveness. A subsequent analysis showed that people with a stronger reading habit is a significant predictor to greater learning effectiveness. Discussions and implications of this study are also presented. © 2013 IEEE.

Chen C.H.,NSYSU | Tang Y.L.,CYUT | Hsieh W.S.,NSYSU | Hsieh W.S.,Slovak University of Technology in Bratislava
Proceedings - 2014 International Symposium on Computer, Consumer and Control, IS3C 2014 | Year: 2014

In this paper, we describe an authentication and recovery scheme for color image protection based on adaptive encoding. The image blocks are categorized based on their contents and different encoding schemes are applied according to their types. Such adaptive encoding results in better image quality and more robust image authentication. The approximations of the luminance and chromatic channels are carefully calculated, and for the purpose of reducing the data size, the differential coding is used to encode the channels with variable size according the characteristic of the block. The recovery data which represents the approximation and the detail of the image is embedded for data protection. The necessary data is well protected by using the error correcting coding (ECC) and duplication. The experimental results demonstrate that our technique is able to identify and localize image tampering, while preserving high quality for both watermarked and recovered images. © 2014 IEEE.

Lee H.H.,NSYSU | Wu T.-C.,NSYSU | Wu Z.-Y.,NSYSU
Applied Mechanics and Materials | Year: 2014

In this study, a new type of energy converting system is developed and installed in an offshore platform structure to take the advantage of strong motion of the platform subjected to waves. It is a device that by utilizing the sloshing power of the fluid stored in a U-shape tube, the turbine of the electric power generator is driven and electricity can be generated. By following previous experimental studies in basic vibration behavior for the FSWECS device that under various periods and amplitudes of the stroke in the experimental tests, can effectively convert vibration motion into electricity power, a further test for the effectiveness of energy converted from the FSWECS device was performed in a water-tank. Parameters identified in previous studies including the natural periods of the FSWECS device, the strokes of the vibration and the relationship between the amount of the liquid filled in the tube and the dynamic character of the device are further studied when subjected to a simulated wave. © (2014) Trans Tech Publications, Switzerland.

Lee H.H.,NSYSU | Wang C.-W.,NSYSU
Advanced Materials Research | Year: 2013

For an infrastructure construction located in marine environments, maintaining good durability for the structures always imposes serious challenges, especially for the structure made of reinforced concrete. Concrete exposed to marine environment may deteriorate as a result of combined effects of both physical and chemical actions from marine environment. Corrosion of the reinforced steel bars that are embedded in the concrete is the most serious problem. Therefore, a method to protect the reinforced concrete in the marine environment from damages due to material deterioration and corrosion is proposed in this study. The method is through the application of bentonite material by utilizing its very finely divided form so that the larger capillary pores in concrete can be filled up. In this way, the impermeability of concrete material can be enhanced and then improve the corrosion resistant ability of the material. © (2013) Trans Tech Publications, Switzerland.

Yu J.C.S.,NSYSU | Chen P.,NSYSU | Yu H.-C.,NSYSU
OCEANS'10 IEEE Sydney, OCEANSSYD 2010 | Year: 2010

A three-dimensional numerical model has been constructed for simulating the hydrodynamics and the biogeochemical responses in coastal lagoons. The model has been applied to study the eutro-dynamics in Dapeng Bay, southwest of Taiwan. Dapeng Bay is the largest single entry lagoon in Taiwan with a area more than 530 ha. The hydrodynamics in the lagoon is dominated mainly by tidal variations from the coastal seas through a tidal inlet during the dry season. Fresh water discharged into the lagoon is concentrated at the rainy season that comes with the southwest monsoon during summer. Constant freshwater sources are untreated domestic sewerages and aquaculture drainages surrounding the lagoon throughout the year. Vertical structure of the hydrodynamics are considered in order to take density effect into account, thus salinity and temperature has to be calculated for computing currents. The lagoon was an important fishery ground where various aquaculture activities had been settled, mainly oyster farming and cage net farming. An eutro-dynamic model has been constructed and coupled with the hydrodynamics for studying the water quality and the eutrofication conditions in the lagoon. Eight state variables have been included in the bio-geochemistry model, i.e. micro-plankton, detritus, dissolved nutrients and dissolved oxygen. The plankton growth is controlled by water temperature, light intensity and the nutrient supplies. The basic assumption for nutrient supply was that Silicate and phosphate are fully available in the lagoon. Therefore, the model only simulates the nitrogen cycle of the lagoon. Tides predicted by a regional model are used for specifying the level at the mouth of the lagoon. Various boundary conditions are obtained from measurements. The responses of the eutro- dynamics to weather and anthropogenic influences are discussed in this paper. © 2010 IEEE.

Lee H.H.,NSYSU | Chen Y.-S.,NSYSU | Cheng C.-W.,NSYSU
Advanced Materials Research | Year: 2012

Concrete as a most popular construction material has many advantages such as easiness to be formed into various shapes, common availability and relative low cost. However, the low tensile strength and brittleness are disadvantages for wider application of the material. In this study, an advanced material of high strength and strong abrasion resistance HMPE fiber was used to reinforce concrete properties. A series of experimental testing were carried out to examine the properties of both fresh and hardened HMPE fiber reinforced concrete. It was found that the addition of an HMPE fiber material in concrete may enhance its compressive strength as high as 20% increment without water-reducing admixture. If a water-reducing admixture was applied, the increment of compressive strength may reach as high as 25% for 1.5% volume ratio of fiber content in concrete. © (2012) Trans Tech Publications, Switzerland.

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